This is just my list, yours is just as valid
If enough -1/-1 counters are put on Hei Bai at the same time to make his toughness 0 or less, his last ability will see all of the +1/+1 counters he had when he left the battlefield as well as the -1/-1 counters he had, and an equal number of each of those types of counters (plus any other applicable counters) will be put onto the target creature
There's nothing this splashable three-drop won't do - make a token, ramp with Treasures, card flow, and make powerful copy makers
Then in your end step exile a random card from all foes, cast it for free, and then they eat damage equal to its cost - amazing free stuff and game winning life loss too
Giving Brain Freeze the escape ability lets you pay 2 mana, mill three cards, and cast Brain Freeze again by exiling three more cards, and so on
If you do, you get the city's blessing