Were you looking for the Baseplate card?
Baseplate is one of BLOX Cards' many game mechanics. It was introduced in Storexit.
Every time either player discards their first colored (non-Colourless) card each turn that generates icons when discarded, that card goes into their Baseplate. Cards in the Baseplate generate a stud of their Type at the end of the turn. This is important because your Coloured studs will always reset to 0 at the end of each turn.
There's no limit on how many cards you can put into the Baseplate. The more cards you are able to put there that aren't inert in Baseplate, the stronger the cards you're able to summon or cast, so it's a good idea to usually discard at least one card per turn. (However, if you have enough coloured studs to cast everything, or have less than 5-4 cards in your hand, it's usually not a good idea to discard.)
Not only does the Baseplate allows you to cast bigger cards, it also benefits certain cards like Papasmurf and Gangmanstyle556 being able to summon extra fighters if there are any specific fighters in the Baseplate. Even Groups like Titans benefit from this by being able to reduce their base cost of 15 colored studs to a measly low number of 6 colored studs, or the Infurnished, which directly gain more power and effects from having more Infurnished in the Baseplate.
Although, be careful! While not detrimental, every card that a player sends to their Baseplate can be valuable information for their opponent's. As an example: While discarding a RukatuKDH on a Lifegain deck may be a good idea depending on the situation, you're also giving your opponent information that a 2000/2000 won't be played in this entire match, giving them less of a reason to "save" that hard removal when such a threat won't exist. (That's why it's a good idea to check your opponent's Baseplate once in a while.)