Swamp

Anrakyr the Traveller

Lord of the Pyrrhian Legions — Whenever Anrakyr the Traveller attacks, you may cast an artifact spell from your hand or graveyard by paying life equal to its mana value rather than paying its mana cost.

Mountain

The Golden Throne

Arcane Life-support — If you would lose the game, instead exile The Golden Throne and your life total becomes 1.
A Thousand Souls Die Every Day — {T}, Sacrifice a creature: Add three mana in any combination of colors.

Trazyn the Infinite

Deathtouch
Prismatic Gallery — As long as Trazyn is on the battlefield, it has all activated abilities of all artifact cards in your graveyard.

Drach'Nyen

Echo of the First Murder — When Drach'Nyen enters, exile up to one target creature.
Daemon Sword — Equipped creature has menace and gets +X/+0, where X is the exiled card's power.
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Imotekh the Stormlord

Phaeron — Whenever one or more artifact cards leave your graveyard, create two 2/2 black Necron Warrior artifact creature tokens.
Grand Strategist — At the beginning of combat on your turn, another target artifact creature you control gets +2/+2 and gains menace until end of turn.