Tetravus | Magic: The Gathering
Formats Tetravus is Legal in
Official Oracle Text for Tetravus
Tetravus enters the battlefield with three +1/+1 counters on it.
At the beginning of your upkeep, you may remove any number of +1/+1 counters from Tetravus. If you do, put that many 1/1 colorless Tetravite artifact creature tokens onto the battlefield. They each have flying and "This creature can't be enchanted."
At the beginning of your upkeep, you may exile any number of tokens put onto the battlefield with Tetravus. If you do, put that many +1/+1 counters on Tetravus.
Official Rulings for Tetravus
10/4/2004 : Any +1/+1 counter which is on this card can be turned into a Tetravite token. It does not care where the +1/+1 counter came from.
10/4/2004 : Only Tetravites from this specific Tetravus may be used for the ability. Ones from a different Tetravus can't.
8/1/2008 : This card now has two upkeep-triggered abilities. Its controller chooses the order they are put on the stack, and thus the order in which they resolve each upkeep.