With 0 cost for the ability, effigy is superior to squid in nearly every case. One squid can control 3 (or 4) seperate creatures at the cost of 2
a turn. If we add more squids, this is multiplied by the number of squids.
On the other hand, one effigy can control three creatures at the cost of 0 a turn. If we add more effigies, we exponentially increase the power, as two effigies can control 6 separate creatures in a single turn, and that lasts for 2 turns-- meaning 12 creatures controlled by 2 effigies. With three effigies, it's 3 creatures for 3 turns, so 27 creatures-- that's locking down the entire board with 3 effigies. The higher base cost doesn't compensate enough for the increase in utility.