Arcane Signet

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

Plains

Selesnya Signet

Toxic Deluge

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

Nature's Claim

Destroy target artifact or enchantment. Its controller gains 4 life.

Sol Ring

Forest

Command Tower

Bovine Intervention

Destroy target artifact or creature. Its controller creates a 2/2 white Ox creature token.

Barbara Wright

History Teacher — Sagas you control have read ahead. (As a Saga enters, choose a chapter and start with that many lore counters. Skipped chapters don't trigger.)
Doctor's companion (You can have two commanders if the other is the Doctor.)

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

Martyr's Bond

Whenever Martyr's Bond or another nonland permanent you control is put into a graveyard from the battlefield, each opponent sacrifices a permanent of their choice that shares a card type with it.

Ian Chesterton

Science Teacher — Each Saga spell you cast has replicate. The replicate cost is equal to its mana cost. (When you cast that Saga, copy it for each time you paid its replicate cost. Copies of Saga spells become tokens.)
Doctor's companion (You can have two commanders if the other is the Doctor.)

Farewell

Choose one or more —
• Exile all artifacts.
• Exile all creatures.
• Exile all enchantments.
• Exile all graveyards.

Narci, Fable Singer

Lifelink
Whenever you sacrifice an enchantment, draw a card.
Whenever the final chapter ability of a Saga you control resolves, each opponent loses X life and you gain X life, where X is that Saga's mana value.

Path to Exile

Exile target creature. Its controller may search their library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Golgari Signet

Claws of Gix

{1}, Sacrifice a permanent: You gain 1 life.

Snuff Out

If you control a Swamp, you may pay 4 life rather than pay this spell's mana cost.
Destroy target nonblack creature. It can't be regenerated.

Feed the Swarm

Destroy target creature or enchantment an opponent controls. You lose life equal to that permanent's mana value.