Guildpact Training Grounds

When this artifact enters, exile any number of
creatures you control until it leaves the battlefield.

At the beginning of your upkeep, put a +1/+1
counter on each creature exiled by this artifact.

{t}, Remove three +1/+1 counters from among
exiled creatures you control: Put a deathtouch, first
strike, flying, haste, or trample counter on an
exiled creature.