Detecting changes to Command Demon
 

Command Demon is modified by the currently summoned demon or by using Grimoire of Sacrifice. It is then replaced by a new spell, though IsSpellKnown and IsPlayerSpell both always return false with the ID of the gained spell. Is there some API to get this info?

Which info are you trying to get? Do you want to know which pet you have summoned? Do you want to know whether you have Grimoire of Sacrifice? Do you want to get the text for the current effect from Command Demon?

I want to know the spell that replaced Command Demon. I'm particularly interested in Singe Magic, which is the spell the warlock gets when she sacrifices the imp. IsSpellKnown(132411) and IsPlayerSpell(132411) both return false.

What does GetSpellInfo(119898) return?

Hah, nice one Phanx, the third return (the texture) is different: spell_fel_elementaldevastation when Singe Magic is available. Thank you!