The title says it all. I think it would add some interesting functionality to encounters. When an NPC casts a specified spell, EVENT_NPC_CAST will listen. I can try to write this but I think it could be done much faster and efficiently in the hands of a skilled dev.
Here's an example of what I mean:
Code:
sub EVENT_NPC_CAST {
if($spell_id == "31") {
quest::say("Har har! I am casting spell id: $spell_id.");
}
if($spell_id == "32") {
quest::say("Ninja, VANISH!");
quest::depop();
}
}