Sol Ring

Carnival of Souls

Whenever a creature enters the battlefield, you lose 1 life and add {B}.

Deadeye Navigator

Soulbond (You may pair this creature with another unpaired creature when either enters the battlefield. They remain paired for as long as you control both of them.)
As long as Deadeye Navigator is paired with another creature, each of those creatures has "{1}{U}: Exile this creature, then return it to the battlefield under your control."

Pitiless Plunderer

Whenever another creature you control dies, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Command Tower

{T}: Add one mana of any color in your commander's color identity.

Armageddon

Ratchet, Rescue Racer

Living metal (As long as it's your turn, this Vehicle is also a creature.)
Lifelink
Whenever one or more nontoken artifacts you control are put into a graveyard from the battlefield, convert Ratchet. This ability triggers only once each turn.

Ratchet, Field Medic

More Than Meets the Eye {1}{W} (You may cast this card converted for {1}{W}.)
Lifelink
Whenever you gain life, you may convert Ratchet. When you do, return target artifact card with mana value less than or equal to the amount of life you gained this turn from your graveyard to the battlefield tapped.

Ratchet, Field Medic // Ratchet, Rescue Racer

Doomsday

Search your library and graveyard for five cards and exile the rest. Put the chosen cards on top of your library in any order. You lose half your life, rounded up.

Toxic Deluge

As an additional cost to cast this spell, pay X life.
All creatures get -X/-X until end of turn.

Arcane Signet

Bottle Gnomes

Sacrifice Bottle Gnomes: You gain 3 life.

Oloro, Ageless Ascetic

At the beginning of your upkeep, you gain 2 life.
Whenever you gain life, you may pay {1}. If you do, draw a card and each opponent loses 1 life.
At the beginning of your upkeep, if Oloro, Ageless Ascetic is in the command zone, you gain 2 life.