Exotic Orchard

{T}: Add one mana of any color that a land an opponent controls could produce.

Sol Ring

Command Tower

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

Arcane Signet

Reliquary Tower

You have no maximum hand size.
{T}: Add {C}.

Xyris, the Writhing Storm

Flying
Whenever an opponent draws a card except the first one they draw in each of their draw steps, create a 1/1 green Snake creature token.
Whenever Xyris, the Writhing Storm deals combat damage to a player, you and that player each draw that many cards.

Cultivate

Search your library for up to two basic land cards, reveal those cards, put one onto the battlefield tapped and the other into your hand, then shuffle.