If a creature is Polymorph’d into a 1HP critter and is hit with a Life Drain effect, do they make the save as the critter or as their default self that the damage knocked them back to? How does max HP reduction interact? I believe conditions carry over, so if that's true you would carry it over and apply it to original form

— Mike Mearls (@mikemearls) September 14, 2018

But would you save as the critter or as yourself? If you saved as the critter and your critter’s max HP was reduced to 0 would you die? save as form you are in when effect hits – if it came along with the damage, I would save before applying damage, then when hit 0 revert to original form for hitting 0 hp

— Mike Mearls (@mikemearls) September 14, 2018

It depends on the particular creature. A wight’s Life Drain inflicts damage first and then forces you to make a saving throw. You’d calculate the damage using the beast’s resistances and immunities, subtract HP, revert to your original form and then make the save. Both forms have separate max HP pools so a reduction doesn't carry over from one form to the other. https://t.co/4vFk26y06w

— Armando Doval (@armando_doval) September 14, 2018

there we go!

— Mike Mearls (@mikemearls) September 14, 2018