Elmar, Ulvenwald Informant

Haste
Whenever you cast your second spell each turn, untap target creature, then investigate. (Create a colorless Clue artifact token with "{2}, Sacrifice this artifact: Draw a card.")
Friends forever (You can have two commanders if both have friends forever.)

Forest

Arcane Signet

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

Three Visits

Search your library for a Forest card, put it onto the battlefield, then shuffle.

Snow-Covered Island

Decanter of Endless Water

You have no maximum hand size.
{T}: Add one mana of any color.

Plains

Snow-Covered Plains

Hargilde, Kindly Runechanter

{T}: Add {C}{C}. Spend this mana only to cast artifact spells or activate abilities of artifacts.
Friends forever (You can have two commanders if both have friends forever.)

Snow-Covered Mountain

Command Tower

Sol Ring

Forensic Gadgeteer

Whenever you cast an artifact spell, investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")
Activated abilities of artifacts you control cost {1} less to activate. This effect can't reduce the mana in that cost to less than one mana.