Darth Sion, Hate-Bound

Undying Hatred - Whenever Darth Sion, Hate-Bound dies, you get an experience counter, then you may pay 2 life. If you do, return it to the battlefield and put X +1/+1 counters on it where X is half the number of experience counters you have rounded down.

Once you have 10 or more experience counters, exile Darth Sion, Hate-Bound.
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Struck down a myriad times by the Jedi, the Sith Lord of Pain managed to retain his decaying body, channeling his hatred into agonizing immortality.