I don't think it causes an attack. That would be like a free skyblitz costing 1
.
Add purify, poisons, Acceleration/Overdrive to the list.
It should remove "summoning sickness" from creatures, but does it re-enable abilities already used that can only be used once per turn?
Depending on the answer to this, cost could need a serious increase (just think of Pharaoh/Scarab...)
Other than that it's a great idea indeed.