A sorcerer in our group is quite fond of using polymorph to change herself into a giant ape (MM page323). At one point in our game last night she managed to grapple a Bheur (Winter Hag), that was riding a Nightmare (flying evil Pegasus). And during the fight the mount was killed sending them all into a 1200ft nose dive which did 120d6, (311dmg) to her polymorphed Ape form, which was it turned out exactly 3 points from killing her instantly with the massive damage rule (PHB page197).
An argument about the damage rule ensued, which I felt was squared away with simple math, but it then lead directly to another argument over the fact that she got to remain in her Giant Ape form because she still had the spell Death Ward active on her sheet. This might have just been simple confusion over how much time had passed after their long rest, as in her case she had Death Ward active for 16 total hrs, not 8, because of the divine sorcerer's "Extended Spell" metamagic (PHB page102).
The argument then CONTINUED to the entire table's near complete exasperation, as it became a debate over whether, or not, she should be reverted back to her original Sorceress form because she hit 0hp (which triggered the ward), or if she never actually hit 0hp because ward keeps you at 1hp.... Ugh
I made a ruling at the table that yes, she's going to continue on as a giant ape at 1hp despite taking over three hundred damage, regardless of how "ridiculous" the other players found it to be because those are the rules and also: "Because: MAGIC". But the RAW question that's now eating at me is: Does the spell Death Ward keep you at 1hp after you technically hit 0hp, or do you just never go below 1hp?