Creeping Bloodsucker

At the beginning of your upkeep, this creature deals 1 damage to each opponent. You gain life equal to the damage dealt this way.

Riveteers Overlook

When this land enters, sacrifice it. When you do, search your library for a basic Swamp, Mountain, or Forest card, put it onto the battlefield tapped, then shuffle and you gain 1 life.

Shelob's Ambush

Target creature gets +1/+2 and gains deathtouch until end of turn. Create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this token: You gain 3 life.")

Cauldron Familiar

When this creature enters, each opponent loses 1 life and you gain 1 life.
Sacrifice a Food: Return this card from your graveyard to the battlefield.

Servant of Tymaret

Inspired — Whenever this creature becomes untapped, each opponent loses 1 life. You gain life equal to the life lost this way.
{2}{B}: Regenerate this creature.

Forest

Pest Mascot

Trample
Whenever you gain life, put a +1/+1 counter on this creature.

Radiant Fountain

When this land enters, you gain 2 life.
{T}: Add {C}.

Swamp

Elves of Deep Shadow

{T}: Add {B}. This creature deals 1 damage to you.

Fyndhorn Elves

Marauding Blight-Priest

Whenever you gain life, each opponent loses 1 life.

Dark Ritual

Blood Researcher

Menace (This creature can't be blocked except by two or more creatures.)
Whenever you gain life, put a +1/+1 counter on this creature.