Even though these abilities are random, I don't think players should play him unprepared, and so I decided to list out his abilities. After much testing, I've only discovered 4 abilities:
1. All other characters get Poisoned 2.
2. All other characters have their stats reduced to 0/1 until the end of the turn.
3. All other characters gain +4/+4 until the end of the turn.
4. All other characters you control are healed for 2, and all enemy–controlled characters take 2 damage at the end of the turn.
Can a dev confirm this, or are there more abilities?