Can Foxfire be played with zero targets (e.g., when hidden in a battlefield with no valid targets, just to pump a Ravenbloom in a showdown)?

Ruling: Yes, Foxfire can be played with zero targets. Any effect that contains "any number" or "up to" can select zero targets, and if zero targets are chosen, the spell or ability can be played without any targets.

Nuances:

• When targeting, units must initially meet the targeting criteria (4 might or less for Foxfire)
• If you choose zero targets with "any number" wording, you don't need any valid targets to play the card
• All units you target must die when the effect resolves (no "may" clause to choose which ones)
• If might values change between targeting and resolution, and targets now total more than 4 might combined, you cross off some targets to get back down to the 4 might threshold