Haldan, Avid Arcanist

Half of a machine that does nothing until its other half runs. This 1/4 Wizard is the payoff end: it lets you play lands and cast noncreature spells from among your exiled cards that carry fetch counters, and it treats mana as any color when paying for those spells. What it cannot do is make a single counter. That work belongs to Pako, Arcane Retriever, the partner it tutors into hand on entry, whose combat damage exiles cards off the tops of libraries and stamps them with the fetch counters this Wizard cashes in. The design deliberately splits one engine across two legendary bodies: one does the digging and marking, the other the casting and fixing, and neither half amounts to much on its own. That interdependence is the whole point of the pairing. It also quietly widens your card pool: Pako exiles from any library at the table, so the counters can land on lands and noncreature spells from decks you never built, and the color-laundering clause means an off-color exiled bomb is castable regardless of your manabase (any creatures caught in the exile pile stay stranded, since this half only unlocks lands and noncreature spells). Partner-with usually just staples two commanders together for a color-identity discount. Here it wires an actual loop, where the two halves are the input and the output of the same process.