dungeon mayhem card sleeves "Dungeon Universalis"+ Expansions Compatible Sleeve Bundle (8803 X 7, 8810 X 8, 8816 X 3) Transparant Card Game Premium Sleeves for Board/Cardgame (87x112 mm) Ryker | 5-Minute Dungeon Card

This costs 6, it's colorless so it can be played in any Commander deck regardless of color

Unlike other Secret Lairs that simply reskin existing Magic cards, this one offers eight unique cards and a special Clue token

The lowest grade recorded for this card (5) sold for $5,100 in 2020

Brave the Elements You need to be in mono-white to properly leverage Brave the Elements, but it makes up for the restriction with efficiency

The price per card isn't quite as good as that of Battle Pack 3: Monster League or Shadow Specters: 1st Edition, but you're unlikely to see as many duplicates, and if there are only a few cards you're hoping to find, there's a chance you'll pull them in your first couple of packs anyway