Arcane Signet

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

Altar of the Lost

Altar of the Lost enters tapped.
{T}: Add two mana in any combination of colors. Spend this mana only to cast spells with flashback from a graveyard.

Exile target creature you control, then return that card to the battlefield under its owner's control.
Draw a card.

Draw X cards, then discard X cards. Create a 1/1 white Spirit creature token with flying for each card type among cards discarded this way.

Copy target instant or sorcery spell, then return it to its owner's hand. You may choose new targets for the copy.

Spells can't be countered.
Each instant and sorcery card in your graveyard has flashback. The flashback cost is equal to that card's mana cost.