Swarm of Rats

Flying (This creature can't be blocked except by creatures with flying or reach.) 1U: Return this creature to its owner's hand.

(T: Add G.)

Whenever an opponent taps a Mountain for mana, you may gain 1 life.

Reach (This creature can block creatures with flying.) Sacrifice a land: This creature deals 1 damage to each creature with flying.

BB, Pay half your life, rounded up: Destroy target nonblack creature. It can't be regenerated.

(T: Add G.)

If you control a creature, damage that would reduce your life total to less than 1 reduces it to 1 instead.