Quarum Trench Gnomes

{T}: If target Plains is tapped for mana, it produces colorless mana instead of white mana. (This effect lasts indefinitely.)

Golos, Tireless Pilgrim

When Golos, Tireless Pilgrim enters, you may search your library for a land card, put that card onto the battlefield tapped, then shuffle.
{2}{W}{U}{B}{R}{G}: Exile the top three cards of your library. You may play them this turn without paying their mana costs.

R&D's Secret Lair

Play cards as written. Ignore all errata.
{T}: Add {C}. (This mana is still added to your mana pool.)