Rulings

If Cruel Celebrant dies at the same time as one or more other creatures and/or planeswalkers you control, its ability triggers for each of them.
If a planeswalker that's also a creature dies, Cruel Celebrant's ability triggers only once.
In a Two-Headed Giant game, Cruel Celebrant's ability causes the opposing team to lose 2 life and you gain 1 life.