As for what a waifu tax is, it is the concept of a card or collectible demanding a higher price tag due to the art showcasing a character deemed as a waifu
Unless you're already in an AFR dungeon when you take initiative, the regular venture mechanic doesnt progress through the Undercity, only the dungeons introduced in Forgotten Realms
The Shift keyword enables players to put out a more powerful version of a character card at a reduced ink cost, if they already have a card in play that matches the requirements
Fountainport As a colorless utility land, you could do worse than Fountainport, which essentially turns all tokens into Clues
For example, you cant sacrifice a Clue token to activate its own ability and also to activate Alquist Proft, Master Sleuths ability
I dont currently have a +1/+1 counter-themed deck that this would nicely fit into