2018-07-13 : Lena’s last ability affects only creatures you control with the appropriate power at the time it resolves. Creatures you begin to control later in the turn won’t gain indestructible, and a creature you control whose power increases later in the turn won’t lose indestructible.

2018-07-13 : The number of nontoken creatures you control is counted only as Lena’s first ability resolves. If Lena is still on the battlefield (and not somehow a token), it will count itself.

2018-07-13 : To determine which creatures gain indestructible while resolving Lena’s last ability, use Lena’s power as it last existed on the battlefield.