I mean, are they susceptible to :
* Flames From The Sky (of From Afar) ? I suppose not, as they are fire resistant... But some spells that should have elemental damage sometimes have "generic" damage, so ..
* Purgatory ? The spell description only talks about undead, but shouldn't devils be affected also ? Devils are "kinda" undead since Dom1, so maybe they are, and things like Holy Pyre, Marignon capitol site, Flambeau or Herald Lance affect both...