Silas Renn, Seeker Adept

To have two commanders, both must have the partner ability as the game begins. Losing the ability during the game doesn't cause either to cease to be your commander.

Once the game begins, your two commanders are tracked separately. If you cast one, you won't have to pay an additional {2} the first time you cast the other. A player loses the game after having been dealt 21 damage from any one of them, not from both of them combined.

You pay the costs for the target artifact card if you cast it. You may pay alternative costs rather than the card's mana cost.

Silas Renn doesn't change when you can cast the target artifact card. For example, if you target an artifact card without flash, you can cast it only during your main phase when the stack is empty.

If your Commander deck has two commanders, you can only include cards whose own color identities are also found in your commanders' combined color identities. If Falthis and Kediss are your commanders, your deck may contain cards with black and/or red in their color identity, but not cards with green, white, or blue.

If you don't cast the card, it remains in your graveyard.