The spell False Life gives you a small amount of temporary hit points. If you cast it multiple times, does the temporary HP stack?
It will not stack with temporary hit-points. However, temporary hit-points that are not temporary hit-points (Arcane Ward, Wizard Arcane Tradition: Abjurer) will stack, as it is a seperate entity that behaves like temporary hit-points. It is not THP, but takes damage for you and cannot die. Therefore, it, and as far as I know only it, will stack with False Life. Polymorphing is not THP, but it behaves similarly so in theory the maximum 'temporary' hit-points you could have would be being Arcane Warded, Polymorphed and False Lifed.