Guild shards is played with a dual color EDH deck, a Spellboard containing 5 different instant and/or sorcery cards with <=2 cmc for each color not in the EDH Deck (15 total), and an emblem used to interact with the spellboard.

The emblem contains two abilities one is an activated ability that allows casting of the cards and the other is a triggered loss condition tied to the player's spellboard:

"3: Cast a card at random from your Spellboard without paying it’s mana cost. If the spell contains X in its mana cost you may pay X as though it were an additional cost. Activate this ability only once per turn. (You may pay any additional costs of the card such as kicker as you cast it.)"

"At the beginning of your end step if there is not at least one card of each color not present in your general’s color identity in your Spellboard, then you lose the game."

The game is played the same as with EDH (40 life, 21 general, 15/20 poison).

Cards cast from the spellboard go on the stack and can be responded to as normal, The interaction with the cards in other zones hasn't been finalized so there are 3 variants for handling the cards:
*Exile the cards when they would leave the stack either by resolution or otherwise.
*The cards go to either the graveyard, library, hand, or exile based on where they or another effect would put them when they leave the stack (advanced play)
*Put them under the emblem in the command zone and make the emblem count up to the number of each color for the loss trigger.

Other variants we have tried as well are:
*Tricolor EDH with 10 cards in the spellboard.
*No activation limits but only 2 cards per color with CMC <=3
*Activation cost of 2 instead of 3