Dummies are units based off simple units that cast spells for the player and is not seen, dummies should have abilities => Invunerability, Ghost, Locust, so it's invunerable, invisible and untargetable
You'll also need to either add mana to your dummy or take the mana cost from the spell the dummy needs to cast. Then just use triggers to put it all together
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.