If Kaisa Evolutionary is in base and you move a unit out of a battlefield you already scored this turn, then send Kaisa to re-take that battlefield, does her on-conquer ability trigger to let you play a spell from trash?

Ruling: No, Kaisa's ability does not trigger. Conquering is a form of scoring, and you cannot conquer a battlefield you've already scored this turn.

Sequence:

• If you attempt to re-take a battlefield you've already scored, a showdown still begins
• If you establish control of the battlefield, you do not get any points or any on-conquer effects

Nuances:

• Conquering only occurs when establishing control of a battlefield that you have not yet scored that turn
• You can still fight for and establish control of a previously-scored battlefield, but it does not count as a conquer