Can you play a reaction when a temporary unit (like a Sprite Mother recruit) dies from the temporary effect?

Ruling: Yes, you can play reactions when temporary triggers at the start of the beginning phase. Both you and your opponent can react to the temporary trigger on the chain.

Nuances:

• If you react by playing a new temporary unit (like with Sprite Call), the new unit will not die immediately. The phase trigger for temporary has already passed, so it won't check again until the next turn.
• If a temporary unit is saved by an effect like Hourglass, temporary will try to kill it again on the next turn.