Najeela, the Blade-Blossom | Nature's Will

Cards

You control at least one creature that can deal unblocked combat damage to an opponent.
You control lands capable of tapping for at least ({W} magic symbol) ({U} magic symbol) ({B} magic symbol) ({R} magic symbol) ({G} magic symbol) .

Attack with your creature.
On combat damage,
Nature's Will triggers, tapping all lands the player you damaged controls and untapping your lands.
Activate
Najeela for ({W} magic symbol) ({U} magic symbol) ({B} magic symbol) ({R} magic symbol) ({G} magic symbol) , untapping your attacking creatures, giving them trample, lifelink, and haste, and adding an additional combat phase after this one.
Repeat.