When Quarry Colossus enters, put target creature into its owner's library just beneath the top X cards of that library, where X is the number of Plains you control.
2014-04-26
If there are fewer than X cards in that player's library, put the creature on the bottom of that library.
2014-04-26
Quarry Colossus's ability is mandatory. If you control the only creatures when that ability triggers, you must choose a creature you control (which could be Quarry Colossus itself) as the target.
2014-04-26
The value of X is determined as the ability resolves. If you control no Plains at that time, put the creature on top of that library.