Professor Hojo's first ability reduces only the amount of generic mana in the first activated ability you activate during your turn that targets a creature
As we alluded to before, these four cards are from The Lost Caverns of Ixalans accompanying Commander set
Dont count Ancient Excavation out
In my first The Dark booster I got Witch Hunter today marked as rare U1 and Ball Lightning another rare U1 and then Maze too in a common
However, if theyre not for you and you want to try and fight treasure heavy decks, you can take a look at my piece on tackling treasures in Commander for some ideas
It just uses the word, "Swamp." Another good example is extort, which has the Black and White symbols in the reminder text, or a fetchland like Mountain Valley that clearly is Red and Green in flavor and mechanically, but is allowed in decks without Red or Green