Noah's Ark

When Noah's Ark enters the battlefield, you may
exile up to two permanents you control of each
color. If you do, Noah's Ark becomes an artifact
creature with power and toughness equal to the
number of permanents exiled this way. Noah's
Ark can't attack and gains indestructible.
{t}, Sacrifice Noah's Ark: Return all permanents
exiled with Noah's Ark to the battlefield. Each
player mills half their library rounded up.