Sheer Drop

Destroy target tapped creature.
Awaken 3—{5}{W} (If you cast this spell for {5}{W}, also put three +1/+1 counters on target land you control and it becomes a 0/0 Elemental creature with haste. It's still a land.)

Serene Steward

Whenever you gain life, you may pay {W}. If you do, put a +1/+1 counter on target creature.

Stone Haven Medic

Drana's Emissary

Flying
At the beginning of your upkeep, each opponent loses 1 life and you gain 1 life.

Tainted Field

{T}: Add {C}.
{T}: Add {W} or {B}. Activate only if you control a Swamp.

Kalastria Nightwatch

Whenever you gain life, Kalastria Nightwatch gains flying until end of turn.

Syndic of Tithes

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.)

Defiant Bloodlord

Flying
Whenever you gain life, target opponent loses that much life.

Wall of Essence

Defender (This creature can't attack.)
Whenever Wall of Essence is dealt combat damage, you gain that much life.

Aerial Responder

Vow of Duty

Enchant creature
Enchanted creature gets +2/+2, has vigilance, and can't attack you or planeswalkers you control.

Sorin's Thirst

Sorin's Thirst deals 2 damage to target creature and you gain 2 life.

Vampire Nighthawk

Flying
Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Nirkana Assassin

Whenever you gain life, Nirkana Assassin gains deathtouch until end of turn. (Any amount of damage it deals to a creature is enough to destroy it.)

Plains

Mortify

Blighted Steppe

{T}: Add {C}.
{3}{W}, {T}, Sacrifice Blighted Steppe: You gain 2 life for each creature you control.

Malakir Familiar

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

Felidar Sovereign

Vigilance (Attacking doesn't cause this creature to tap.)
Lifelink (Damage dealt by this creature also causes you to gain that much life.)
At the beginning of your upkeep, if you have 40 or more life, you win the game.