Due to the rules of the divine, most characters in the Ars Magica game will probably pass into a final death without God’s blessing. Their ghostly forms might roam the afterlife, until whatever judgement gives them release. I had a thought after creating a spell to torture a ghost that it would also be plausible to artificially give a ghost a pleasant afterlife using magic.
Blessing of Eternal Joy
Rego Mentem 35, R: Arc, D: Ring, T: Individual
This spell connects the caster to ghost of a dead person for whom they possess the arcane connection (or body), and changes the ghost’s mental state to one of happiness and joy.
(Base 5 to control a natural emotion, +4 Arc, +2 Ring)
This happiness spell could also be used before opening discussion with a ghost to make them more receptive to questions and requests, and might be considered more moral than torturing a ghost for answers.
To really be effective for an extended time the effect should really be constructed into a coffin which holds the earthly remains of the target. This way it always has access to the arcane connection, and it is (hopefully) harder for somebody to tamper with it.
The effect to suspend the rot of the corpse could use the same ring as the main effect.
Circle Against Purification
Creo Corpus 5, R: Touch, D: Ring, T: Individual
Prevents the decay of a human corpse, or a severed body part, while the Ring is maintained and the target remains within it.
This spell is a simple re-working of Charm Against Purification (ArM p129) with the duration altered to Ring.
(Base 2, +1 Touch, +2 Ring)