Tetravus gets three +1/+1 coutners when cast. During your upkeep,
you may move each of these counters on or off of Tetravus.
Counters moved off of Tetravus become independent 1/1 flying
artifact creatures. If such a creature dies, the counter is removed
from play. Such creatures may not have enchantments cast on
them, and they do not share any enchantments on Tetravus.