I have read that the polymorph and power word kill spell combo can be annoying for DMs but I'm confused on why it works.
In the description for the polymorph spell it states:
The transformation lasts for the duration, or until the target drops to 0 hit points or dies.
When it reverts to its normal form, the creature returns to the number of hit points it had before it transformed. If it reverts as a result of dropping to 0 hit points, any excess damage carries over to its normal form.
When a polymorphed creature dies from power word kill, shouldn't it revert back to its normal form with its previous number of hit points?
How does the power word kill spell affect a creature with polymorph cast on it (whose new form has less than 100 HP)?