To get a dummy to cast an ability, you must order it to cast the ability it is based off of. Sound simple? Let me simplify it further via an example:
-Me: Dum dee dum dee doo... I would like my unit to cast Storm Bolt when I cast Cripple! But I want it to look like... a firebolt! That's never been done before! (Notice the cleverness)
-Me: Let's open up the Object Editor... ooh, let's pop open Storm Bolt. Change a few fields, the icon, art, and let's change the name to Dummy Storm Bolt For Cripple Ability so I know how to reference it later!
-Me: *opens up Trigger Editor* Add the event, the condition, set GeneralPoint, create the dummy, add the expiration timer, add the ability, set the level... what? I can't make my unit cast Dummy Storm Bolt For Cripple Ability? All it is listing are the abilities that came with the game! Bug!
-Me: Okay, let's back up. It looks like a firebolt, let's try Neutral -- Firebolt. *tests* No! My dummy didn't do it! Noez!
And of course, by now you have realized that my dummy should be casting Storm Bolt; it may not be the closest thing to the ability I made, but my dummy ability was based off of Storm Bolt, and as such ordering it to cast Storm Bolt will make it cast the dummy ability.
Anyways, how do you make the Computers to cast custom spells? For example, you make a new spell where you summond 5 furbolgs. If you replace Holy Light with that spell, when you play a game, Paladin is not going to cast the custom spell, how do we fix that?
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.