Flying Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)

Flying {7}{B}, {T}, Sacrifice this creature: Target opponent loses 4 life and you gain 4 life.

Flying Haunt (When this creature dies, exile it haunting target creature.) When this creature enters or the creature it haunts dies, target player loses 2 life and you gain 2 life.

Flying When this creature enters, if you gained life this turn, return up to one target creature card from your graveyard to your hand.

Offspring {B} (You may pay an additional {B} as you cast this spell. If you do, when this creature enters, create a 1/1 token copy of it.) Flying At the beginning of your upkeep, reveal the top card of your library and put that card into your hand. You lose life equal to its mana value.

Flying, lifelink When this creature enters, look at target opponent's hand. You may exile a nonland card from it until this creature leaves the battlefield.

Mutate {4}{B}{B} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.) Flash Flying Whenever this creature mutates, destroy target creature or planeswalker an opponent controls.

Bloodthirst 1 (If an opponent was dealt damage this turn, this creature enters with a +1/+1 counter on it.) Flying

As long as you've lost life this turn, this creature has flying and vigilance. Whenever you gain life, put a +1/+1 counter on this creature. When this creature dies, put its counters on target creature you control.

Flying When this creature dies, learn. (You may reveal a Lesson card you own from outside the game and put it into your hand, or discard a card to draw a card.)

Kicker {3}{B} (You may pay an additional {3}{B} as you cast this spell.) Flying, lifelink If this creature was kicked, it enters with two +1/+1 counters on it.

Flying {B}, Pay 1 life: This creature gets +1/+1 until end of turn.

Flying, first strike, haste

Flying Whenever another creature you control enters, you gain 1 life.

Flying, deathtouch Whenever you gain life, this creature gets +1/+1 until end of turn.

Whenever you gain life, each opponent loses 1 life.

Flying Whenever this creature attacks, you gain 1 life.

Flying Whenever a creature an opponent controls dies, you create a Blood token. (It's an artifact with "{1}, {T}, Discard a card, Sacrifice this token: Draw a card.") Whenever you sacrifice an artifact, put a +1/+1 counter on this creature and you gain 1 life.

Flying, deathtouch Whenever you gain or lose life during your turn, Bats you control get +1/+0 and gain deathtouch until end of turn. This ability triggers only once each turn.

Flying At the beginning of each end step, if you gained life this turn, create a 1/1 black Bat creature token with flying.

Ward {2} As this creature enters, choose a creature type. This creature is the chosen type in addition to its other types. If a triggered ability of another creature you control of the chosen type triggers, it triggers an additional time.

Flying, lifelink At the beginning of your end step, if you descended this turn, scry 1. (You descended if a permanent card was put into your graveyard from anywhere.)

Battle cry (Whenever this creature attacks, each other attacking creature gets +1/+0 until end of turn.) When this creature enters or dies, create a 1/1 black Bat creature token with flying.

Flying At the beginning of your end step, if you gained or lost life this turn, look at the top four cards of your library. You may reveal a creature card with power 3 or less from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

Flying At the beginning of your end step, if you gained or lost life this turn, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Offspring {2}{B} (You may pay an additional {2}{B} as you cast this spell. If you do, when this creature enters, create a 1/1 token copy of it.) Flying This creature can't block. Whenever you gain life, each opponent loses 1 life.

Flying, vigilance At the beginning of your end step, if you gained or lost life this turn, target opponent loses 3 life unless they sacrifice a nonland permanent of their choice or discard a card.

Flying This creature can't block. Blood Drain — {1}{B}, Pay 1 life, Sacrifice this creature: Draw a card.

Whenever one or more other Rabbits, Bats, Birds, and/or Mice you control enter, scry 1. Other Rabbits, Bats, Birds, and Mice you control get +1/+1.

Whenever you gain life, target opponent loses that much life. {3}{B}{B}: Creatures you control gain lifelink until end of turn.

(Gain the next level as a sorcery to add its ability.) If you would gain life, you gain that much life plus 1 instead. {3}{W}: Level 2 Whenever you gain life, put a +1/+1 counter on target creature you control. {4}{W}: Level 3 When this Class becomes level 3, return target creature card from your graveyard to the battlefield. You gain life equal to that creature's toughness.

Sonar Strike deals 4 damage to target attacking, blocking, or tapped creature. You gain 3 life if you control a Bat.