Great Furnace

The artifact land was an experiment in making a mana source double as artifact-count fuel, and this is the red one: it produces a single color while carrying the artifact type on its line, which sounds harmless until you notice that every card counting artifacts now counts your lands too. That overlap, land and artifact at once, eventually wore the cycle out of its welcome in older formats. A land that pads an affinity count, fills a graveyard for artifact recursion, and answers to artifact tutors is structurally different from a basic, even when its mana ability reads identically. The trade-off is genuine: being an artifact exposes it to artifact removal in a way no land normally faces, so a sweeper aimed at your Cranial Plating can take your mana with it. As a design it answered a specific question (how do you let a deck that wants thirty artifacts treat its lands as part of the count) and the answer proved powerful enough to require ongoing format management. The free artifact triggers, the convertible permanent that is land and spell-fodder at once: all of it traces back to the decision to staple a land's job onto an artifact's type line and let the synergies sort themselves out.