Antichickenator is used in BG1 by Thalantyr, when he tries to remove a curse of his apprentice (who was turned to, of course, chicken).
Just ten damage is used by some script that needs to take 10HP away, obviously

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I always thought that MDK2 spell was Easter Egg. Isn't it?
Isn't Gas Spore used by Myconids? Or by something else?