Aetherflux Reservoir

Whenever you cast a spell, you gain 1 life for each spell you've cast this turn.
Pay 50 life: This artifact deals 50 damage to any target.

Plains

Ancestor Dragon

Flying
Whenever one or more creatures you control attack, you gain 1 life for each attacking creature.

Benalish Marshal

Linden, the Steadfast Queen

Vigilance (Attacking doesn't cause this creature to tap.)
Whenever a white creature you control attacks, you gain 1 life.

Healer's Hawk

Flying
Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Arashin Cleric

When this creature enters, you gain 3 life.

Ajani Goldmane

+1: You gain 2 life.
−1: Put a +1/+1 counter on each creature you control. Those creatures gain vigilance until end of turn.
−6: Create a white Avatar creature token. It has "This token's power and toughness are each equal to your life total."

Summary Judgment

Summary Judgment deals 3 damage to target tapped creature.
Addendum — If you cast this spell during your main phase, it deals 5 damage instead.

Knight of the White Orchid

First strike
When this creature enters, if an opponent controls more lands than you, you may search your library for a Plains card, put it onto the battlefield, then shuffle.

Attended Knight

First strike
When this creature enters, create a 1/1 white Soldier creature token.

Gideon, Battle-Forged

+2: Up to one target creature an opponent controls attacks Gideon during its controller's next turn if able.
+1: Until your next turn, target creature gains indestructible. Untap that creature.
0: Until end of turn, Gideon becomes a 4/4 Human Soldier creature with indestructible that's still a planeswalker. Prevent all damage that would be dealt to him this turn.

Kytheon, Hero of Akros

At end of combat, if Kytheon and at least two other creatures attacked this combat, exile Kytheon, then return him to the battlefield transformed under his owner's control.
{2}{W}: Kytheon gains indestructible until end of turn.