Penetration HR for Item Creation using Arcane Connections

In many myths and stories weapons and devices are crafted to hurt specific creatures, or a type of creature. Ars Magica does not specifically support powers meant for classes or types of opponents. Examples like the way Stormbringer from the Elric saga drinks energy, or Sting from the Lord of the Rings warns when orcs are near.

In Ars Magica items can be designed with powers to affect supernatural creatures however often these creatures will have resistance to spells and powers. As Penetration vs MR is the existing mechanic in-play to represent this I think it makes sense to provide options for Penetration which empathise the saga and story aspects of these special tools.

These are the types of proposed special options in item creation in Ars, all which modify how an item calculates its penetration score for a particular power:

  • Prescribed Penetration
  • Entity Penetration
  • Arcane Penetration

Note that if any of these options for additional penetration are used together their effects are not multiplicative, meaning that they modify the base amount of penetration in the enchantment, not the boosted amount.

Prescribed Penetration (+5) – Penetration of invested powers is enhanced when used with the Target for whom the AC applies, and is otherwise ineffective. The goal with this style is to prescribe the type of target and how the AC is used within the enchantment.

This adds half again the Penetration point already invested into the invested power design, however the invested power has zero penetration against other targets.

Invested powers using Prescribed Penetration must declare the material and technique of ACs which can be used and the manner in which the power interacts with the item. The method must also match thematically to the use of the power and item.

i.e. a magical sword could be given a “blood drinking” power to gain enhanced penetration against foes. That invested power could not make use of another AC which wasn’t blood.

The AC need not be “fixed” or permanent, however the AC must be physically touching the item when the power is invoked.

For example: Blood on a sword. Powers invested in a magical blade have enhanced penetration only if the wielder is able to first inflict at least a light would with the blade (or otherwise draw blood of the victim onto the blade).

Entity Penetration (+10) This option links the invested power to a fixed arcane connection to a specific individual, thing, or place. When used this enhances the penetration by doubling the invested base item penetration.

Arcane Penetration (+10) the penetration of the invested effect uses the penetration skill of the person activating the power, as per the Form + Tech + Penetration ability with all normal modifications for the arts of the invested effect rather than points invested in Penetration.

Arcane Penetration also requires that the activator also be touching the magical device when the power with this option is activated, and when a power with this modification is used an arcane connection is formed from the activator to the item for one week per magnitude of the power.


Laboratory Activity without a lab?

Wandering Magi typically have limited access to a laboratory, so will rarely be able to create a lot of spells and items. Enforcing the rules of no-lab-no-results encourages Magi to join covenants and to find novel solutions to not having a readily available laboratory – however I think there is reason to allow Magi some capability to invent spells while away from their labs.

First – I’m happy to acknowledge this breaks the rules, or that the degree of the bonus needs to be changed to suit different games. And yes, it add complexity in a system which is already full of options and rules – YSMV.

The Apprentices source book introduced the idea that casual experience points can be spent on spont cast spells, at a rate of one point per level, to allow a magus (in this case an apprentice, see “Learning Cantations in Play” in Apprentices p.46) to learn a spell gradually. This makes a lot of sense for learning while doing, and when the option is presented among a set of level 3-5 spells it makes sense as they can be purchase cheaply without distracting the apprentice from other learning.

There are several small effects which might also be worth learning. Detecting vis, detecting aura, and a host of other low level spells which are frequently cast spontaneously are great candidates.

aside – Two spells from the Apprentices book look great (p.46-ish) – A Pestilence of Fleas (MuIm4, to itch the target so much they have a -1 on actions) and Whispering Fingers (CrMe5, whisper into the mind of somebody you can touch) are good examples. Both very useful, especially suffering a -1 to a target in combat, or following up a whisper into the mind of your target via an Intangible Tunnel.

Consider that a magus can learn these easily with a lab, and take a season. However that ignores the fact that a season has an opportunity cost for what else could have been done. Could the magus buy these spells instead of invent them themselves? Could these spells be learnt in the same season as others, thereby being stacked for efficiency.

This optional rule “opens the door” as an example of a magus learning a spell without a lab. Using the rules in Apprentices the magus just needs to cast the spell spontaneously and spend xp on it.

I guess that the rationale is that the caster is experiencing the spell and earning its subtle aspects again and again in-Play, so should be able to learn it without a lab eventually.

This seems like a casual way to learn a spell, but what if that magus applies themselves to practicing aspects of a specific more complex effect and devotes time to learning it as a seasonal activity despite not having a Hermetic lab?

As a House Rule a magus can progressively design spells without a lab within the following rough guidelines:

  • If the Magus is trying to invent a spell whilst performing some other activity which takes up most of their time, then the success points accumulated beyond the level of the spell is one fifth its normal value. Always rounded down.
  • If the Magus is distracted by many chores or goals, however they have enough downtime to spend pondering and designing; such as touring safely between a few covenants, or stuck aboard a ship, the success points are divided by four.
  • If the Magus is doing little else except trying to invent a spell however they still lack a lab, such as living at a covenant where a lab space is absent, the success points are divided by three.

Some examples:

A beginning magus with a low-ish lab total around level 25 is seeking to invent a level 5 effect while travelling and camping in the wild. Normally the magus would accumulate 20 success points per season, however the travel, rest, and logistics reduce this total down to 4 per season. The junior Magus is able to scratch away at a minor spell while he travels and hunts for 2 seasons (or a level 10 in five seasons).

A very mature Magus seeks to stay productive while visiting another covenant. The host covenant does not have a guest lab, however the Magus is provided with ample rooms, and the political and social activity is not at all arduous. He returns to his notes on a pet project within his focus and specialty, normally generating a level 65 lab total, on a niche spell at level 20. However his success total is reduced to one third, from 45 down to 15 which is still enough to generate the spell in two seasons (or a level 15 effect in a season, or a level 30 effect in three seasons).

The rationale for this is the Magus is able to gain some success points on a magical activity whilst doing something else, and that they can slowly progress their work. The invention might happen in disjointed seasons, say perhaps one season a year where the Magus travels for some obligation to their apprentice or House – they get some productivity.

Obviously the players need to ratify this suggestion to be used in the Ars game. The intent is to allow a magus to be productive on the same complexity of effect as normal, however to reduce their effective productivity.

And as always I’d like to add a few new spells into the wider community based upon one of the spells in the Apprentices book. A Pestilence of Fleas lends itself to a greater version for combat against groups – perhaps A Carpet of Fleas instead? Sure, not a huge change, but disruptive for crowds and armies.

A Pestilence of Nipping Bugs

Muto Imagonem 10, R: Voice, D: Diameter, T: Group

This sensory illusion makes all the targets itch, any tasks requiring Concentration or physical activity are penalized by –1.

(Base 1, +2 Voice, +1 Diameter, +2 Group)

As an Inagonem spell it isn’t locked to humans or animals…so lots of diversity in use.

A Pestilence of Fleas for Months

Muto Imagonem 10, R: Voice, D: Moon, T: Individual

This sensory illusion makes all the targets itch, any tasks requiring Concentration or physical activity are penalized by –1.

(Base 1, +2 Voice, +3 Moon)

Curse of Imaginary Pestilence

Muto Imagonem 20, R: Voice, D: Until, T: Individual, Faerie, Ritual

This sensory illusion makes all the targets itch and smell of rot, any tasks requiring Concentration or physical activity are penalized by –1, until the caster utters a sentence of forgiveness.

(Base 2, +2 Voice, +4 Until)

Ars Magica house rule – Capping MT scores in labs?


Some characters in ars magica seem to create very specialised characters and in turn, very specialised aides and familiars. This can lead to a slew of high stat NPCs in the game and that adds to both good and bad inflation of lab totals.

One way to curb the growth is to rule that the effective Magic Theory (MT) of each assistant is capped at the lab leaders MT score.

As normal the leader needs to have the gift and also needs to follow the guidelines for how many lab aides they can have according to their Leadership score.

This additional cap would discourage familiars being used as MT xp dumps, and force player Magi to raise their MT as a higher priority. That is certainly a double-edged sword in terms of how a saga might play out.

House Rule for Casting Forcelessly

In Ars Magica Casting a spell forcelessly is a deliberate act by the caster to inhibit their own spell power/spell strength so that they do not risk unintentionally cast a spell on another Magus. I’m not sure what a useful real life comparison might be – however it seems like the wizard is seeking to use enough of their knowledge and power to successfully cast the spell, but absolutely no more. Seems not without some risk.

Is that like quickly physically lifting an object up off the floor only one handspan? Or filling a bottle to the brim but not letting another drop spill? Do it fast but don’t go over.

Sounds like something which should require a basic Finesse check to do properly. Even rated as an easy task (say target value 3+) introduces the potential for mistakes and risk.

(As a counter – Ars Magica is a roll heavy game so perhaps KISS applies)

Perhaps if the Finesse check fails, the Casting Total is calculated normally minus the caster’s Penetration score. Sure, the magus didn’t mean to use a little extra force, but magic is fickle and sometimes hard to control.

On a botch (and this is a skill check and not a magical botch) perhaps the spell is cast as normal including the caster’s penetration skill. Whoops eh?

Images copyright Blizzard Entertainment – WoW BfA (which is what I’m doing to stay sane when I have some spare time and need to explore. Happy killing folks)

Reduced Might Stripping, a House Rule for Ars Magica supernatural opponents


A great house rule to limit the impact of might stripping spell effects on supernatural creatures in Ars Magica – Multiple applications of Perdo Vim do not stack, specifically for reducing a creatures Might or affecting an Arcane Connection. Once damaged only a more powerful spell will inflict more damage. Makes the famailiars tougher too.

Found via a discord group I’ve been chatting to. Clever idea!

Warping Points advancement house rule

A Final Twilight event as a result of extended Warping for Magi is potentially how their lives as characters will end, although to be fair many Magi in my experience are retired by story events, killed, or paused due to a permanent hiatus of the game. In my view warping is something which infrequently impacts a Magus character and very rarely ends their life through Final Twilight.

When advancing a character through their years post-gauntlet in bulk there is a rough rule of thumb to add a few warping points each year due to longevity, strange events and spell casting botches. Two points per year is ok, but does not reflect virtues and flaws, or other game events.

So how many points are reasonable to add per year when advancing a character before play begins?

Here are my suggestion:

  1. Add 1 point per year the character has a Longevity Ritual. This is standard to the core rules.
  2. Add 1 point for each extra virtue or flaw gained though non-Twilight related means (cult initiation, realm of magic, freaky story event in accelerated advancement, etc).
  3. Add 1 point per 5 years (rounding down) if the character has a flaw which makes Twilight more regular or more severe. If the character has more than one of these flaws then they are cumulative.
  4. Add 5 points per 10 years after their Gauntlet; because things go wrong.
  5. Mitigate the total value of item 4 above by subtracting the Familiar’s Golden Bond score; because the cord should greatly reduce the probability of botching.
  6. Further mitigate item 4 if the character has a suitable virtue such as Cautious Sorcerer, reducing by -1 for each.

Hope this is useful.

Substitute Finesse checks with complexity modifiers?

Discussion post – Is it reasonable to add magnitudes into Ars Magica spell designs which substitutes Finesse rolls with complexity modifiers?

By RAW no. However as a house-rule it has merit and also is sort of implied by the core rules before all the expansion rules were added. Playing Ars Magica with Core Only is very different from using all the new rules. In fact playing with all the rules would be mind boggling, so a few more choices to suit how players might want to play isn’t breaking. YSMV.

In the base rule book the Finesse skill is not given the same degree of importance to Creo and Rego magic, specifically because new guidelines were introduced in other books. 

As example – A Rego specialist Magus could be designed with a moderate Finesse in core, but would be next to useless in the expanded (now very RAW cannon) Finesse rules; primarily because the target numbers for Rego crafting magic and by extension Creo magic are ridiculously high.

How high? Well a Finesse check in the mid-20s isn’t uncommon, and 30+ is needed for the really cool stuff. In a game with 1d10+skill(1-6)+stat(1-5) that’s punitive.

I previously wrote about using time as a mitigation for Finesse checks for Creo ritual spells, and I think the suggestion makes sense. Essentially it allows a high degree of preparation to mitigate the Finesse roll, as long as the spell also has a complexity modifier built in (just as Conjuring the Mystic Tower has, which was a spell written before the expanded Finesse rules). This allows a way to rationalise the rules where one ritual spell does not require a Finesse roll, but the instant Rego/Crafting spells still do.

So what about expanding that house-rule to allow additional mags to add a bonus to the Finesse check?

Suggested new Guideline:


Caster gains +3 bonus to the Finesse check for each Magnitude added for Finesse Complexity in spell design. This complexity may only be added where the description also produces a higher quality and beauty item, and must produce a more specific result for each step in magnitude.

I’m a supporter of this principal too, as I see spell complexity as a representation of increasing detail mandated in a spell (as if the spell is an architectural design or a script).

I also like the idea that magic can have many ways to do the same thing, and a spell designer could build knowing that their version of a spell is far higher than another wizards, but they get to an almost identical result.

Along with that Finesse check should be a restriction on the purpose of the spell. A Creo spell to create a sword could have a lot of variety in the result. A ritual using this suggestion to create an ornate and wonderfully crafted sword should note what the additional complexity is for.

This ensure that the complexity added for component parts, or high detail is different from the “complexity for Finesse replacement”.

Quoting from and E.g. from the Atlas Forums by Virgileso:

Echo of Durendal

CrTe 40, R: Touch D: Momentary T: Individual

This spell creates an excellent quality steel longsword, granting the wielder a +4 Attack & Defense in combat due to its uncanny craftsmanship.

(Base 5, +1 Touch, +6 complexity)


Designer’s Notes: Rather than requiring a Finesse check against an EF 30 for such a sword, I am instead obliviating the roll altogether and setting the spell’s crafting total to a flat 12+(3*complexity) against an EF as per the Rego Craft Magic guidelines set forth in Covenants.

I don’t think it’s game breaking. My interpretation of the spell above would be that it will create an identical weapon each time it is cast because the design adds 6 magnitudes for the Finesse bonus.

It is a different style of solution to adding time (above), and while it’s plausible that these options might be used in combination a table of players would probably need to pre-select if either option was allowed and carry that forward in their games.

Happy games folks.