Text (ET): Shroud. ; {X}: Put X tower counters on ~this~. ; At the beginning of your upkeep, if there are 100 or more tower counters on ~this~, you win the game.
It checks for the 100 counters both when the ability triggers and right before it resolves. [Eventide FAQ 2008/07/08]
If it leaves play before the ability resolves, check the number of counters on it at the time it left play. [Eventide FAQ 2008/07/08]
