Mycosynth Lattice makes every permanent an artifact and makes the game's cards, spells, and permanents colorless. It also allows players to spend mana as though it were any color. Those changes can turn narrow artifact interactions into effects that reach nearly the entire battlefield.
Karn, the Great Creator is a powerful partner. Because opposing permanents become artifacts, Karn's restriction prevents their activated abilities from being used, including the mana abilities of their lands. Your own permanents are not restricted by Karn in the same way. The combination requires both pieces to remain present, and removing either can reopen opposing resources.
Artifact protection also expands. Darksteel Forge can give all your permanents indestructible once Lattice makes them artifacts, while artifact removal becomes useful against many more targets. That expansion applies to opponents' removal too, so the Lattice can expose lands and other valuable pieces to effects that ordinarily could not touch them.
The mana permission fixes colors but does not turn colored mana into actual colorless mana for costs requiring a colorless symbol. It also benefits every player, not just you. Six mana is a meaningful setup investment, so include Lattice when the type-changing effect supports a specific plan. A deck that merely wants better color fixing usually has cheaper options; a deck built to exploit universal artifact status can use it to fundamentally change which cards control the board.
