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Counterspell: Disabled since it is a feat (could be a cheat-cast "spell" but cannot be a spell-like ability).
Spell Resistance and Immunity: Currently entirely disabled and not even checked for. Level 10 spells can't be absorbed by Spell Mantles anyway, but spell resistance could still be a thing if we really wanted. Technically Epic Spells have spell resistance checks but that's as proper level 10 spell slots and have most of the standard spell mechanics.
We'd probably fix these to be more like real spells (ie Spell category, cheat-cast etc.) if we wanted to avoid feats and go the NUI route so there is more counterplay (although Counterspell is difficult we shouldn't probably have that!).
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