>>95992571
It was literally the gimmick of Invasion? They brought back gold cards and made a big deal of it - I recall MaRo/whoever articles about how "we do a thing every 10 sets" and multicolor had been absent for all of Saga/Masques - but then also printed split cards, which were technically two single color cards stapled together. Invasion got allied pairs, Apocalypse (which was centerd around enemy colors cooperating and featured enemy painlands) gave us enemy color split cards. They've done callbacks to that mechanic since, including fuse (play both halves at the same time) and recently rooms (pick a side when you cast, pay the other half later). They're the original double-sided cards, I suppose.

Fire // Ice (they're written like that in online catalogues so browsers don't misread them I guess) is infamous because of pic. Extended became instantly unplayable when Mirrodin dropped. You'd think the best option was to put a Counterspell into the Scepter and counter something every turn, but no, you could Fire anything small and Ice anything big/important while also drawing a card, regardless of what color mana you had available. It was Icy Manipulator on steroids, which helped cement my decision to quit.