This means that by turn "X," if you don't have a creature to drop, you are going to fall behind on board development
Effects that last "for as long as that creature has a [kind of] counter on it," such as Aven Mimeomancer's, stop applying to Me, the immortal once it leaves the battlefield
Consider Terminate, Abrade, or Withering Torment
He's in every game except the first, and so Wizards has made a Cid card with 15 different arts
Combined with the frankly outrageous state of things back then (4 Ancestral Recall , anyone?) leading to prolonged game states and impasses, WotC decided that enough was enough and restricted Ivory Tower
Get a decent build around it, and youll have your opponents taking care of each other as you sit back and enjoy the carnage