Devolution
School: transmutation
Level: Arcanist 3, Wizard 3, Sorcerer 3, Summoner 3, Unsummoner 3, Psychic 3
Casting Time: standard action
Components: V, S, M
Range: close (25 feet + 5 feet/2 levels)
Target: eidolon (1)
Duration: 1 round/level
Saving Throw: Will negates
Spell Resistance: yes
Source: Advanced Player's Guide, p. 216
Description
This spell causes an eidolon to lose one evolution plus one additional evolution for every five caster levels. Evolutions with the highest total cost are lost first. If there is a tie, randomly determine which is lost. If this spell causes an eidolon to fail to meet the prerequisites for other evolutions or abilities, those evolutions or abilities are lost as long as this spell persists.
Mythic Devolution
The saving throw changes to Will (partial). If it succeeds at its save, the eidolon loses one evolution, chosen at random.
Mythic Adventures, page 91