Marble Diamond

The white member of the Diamond cycle, a five-color family of two-mana rocks that softened the Moxen template by charging tempo for color access. Where the original artifact accelerants produced free, untapped mana, the Diamonds pay for a single colored source by arriving tapped. That tapped clause is the entire balance: the rock never ramps you on the turn you cast it, only smooths the turns after, which keeps a colorless two-mana artifact from snowballing into the broken starts that faster fixing enabled. That tempo cost is what separates this generation from the signets and talismans that followed, which dropped the tapped restriction in exchange for either filtering or an alternate color. The Diamond offers nothing but a guaranteed white source that costs no life and survives most artifact-light boards; its value is consistency, not speed. It sits at the conservative end of mana-rock evolution, from an era that treated colored mana as something you waited a turn to earn rather than something you stapled to a free body. Reasonable wherever a deck wants a clean, life-neutral white source and can spare the turn it takes to come online.