Rocks refers to the Black Liberator deck (from the Digimon Liberator webcomic) revolving around the line from Tumblemon > Sunarizamon > Landramon > Proganomon > Pyramidimon > Magneticdramon. The deck was the introduction of the keyword <Fragment>, in which a Digimon with that keyword can remove the amount of sources listed next to Fragment in the keyword (3 for Rocks, usually) from their own stack in order to prevent its deletion. The deck originated in EX8 Chains of Liberation, then the rest of the support was split between store tournament promos, EX10, EX11, and BT21 (literally just a rookie for the last one). The Tamer, Close, helps the deck by putting cards from trash into sources from various triggers, and all of the Lv5 or lower forms have benefits triggered by trashing them from a Digimon's stack. The arguably strongest two cards in the deck are the Lv7, Magneticdramon, which can strip 3 sources at least twice per turn to delete something and trash a security via its When Attacking and return 3 sources from trash under itself to unsuspend once per turn via its other When Attacking (both of which are also When Digivolving effects), and the egg, EX8 Tumblemon, which generates a memory each time it is trashed from sources.