Primordial Ooze

This creature attacks each combat if able.
At the beginning of your upkeep, put a +1/+1 counter on this creature. Then you may pay {X}, where X is the number of +1/+1 counters on it. If you don't, tap this creature and it deals X damage to you.

Fifth Edition

Primordial Ooze attacks each turn if able.
During your upkeep, put a +1/+1 counter on Primordial Ooze. Then pay o
X, where X is equal to the number of these counters on Primordial Ooze, or tap Primordial Ooze and it deals X damage to you.

Chronicles Foreign Black Border

Chronicles

Must attack each turn if possible.
At the beginning of your upkeep, put a +1/+1 counter on Primordial Ooze. At the end of your upkeep, pay X, where X is equal to the number of +1/+1 counters on Primordial Ooze, or Primordial Ooze deals X damage to you. If Primordial Ooze deals damage to you in this way, tap it.

The thick, moving mass from the beginning of evolution swallows and digests the animate and inanimate as it unthinkingly strives to continue its existence.

Legends

Must attack each turn if possible. Gains +1/+1 at end of your upkeep. Use counters. Then pay o1 per counter or Ooze deals 1 damage to you for each counter and becomes tapped.

It becomes tapped even if the damage is prevented.