Estra, Inspired Tactician

When Estra, Inspired Tactician enters the battlefield, create a 1/1 white Bird creature token with flying and a 3/3 black Cat creature token.
Attacking creatures you control get +1/+0.
At the beginning of your end step, if at least three creatures attacked this turn, you may pay {x}{w}{b}, where X is the number of opponents dealt combat damage this turn. You gain X life and draw X cards.