Hrothgar Rannúlfr said:I'm very confident that I read, last night, in the Player's Handbook that a Spell-like Ability can be "cast" defensively (just like a spell).
It's in the MM and it can be done the same as a spell (you use the highest SL for the invocation and shape and essences modifiers so for a Hideous Bloww/EB it is treated as a 1st level spell for the check in question).