He was looking at it due to a long-running obsession with discard strategies (look at that name, obviously) and the weird in your hand but cant be Thoughtseized dynamic foretell setup
Hopefully these options give you ideas on how to best handle your storage needs
This card being in Standard again makes you think twice before casting an expensive spell into open blue mana, for example
Counting all cards that care about Dungeons, including ones that Venture and ones that care about if you've completed a dungeon, there are a total of 41 cards
You can go reanimator, you can be a combo deck with Opposition Agent (who is a Rogue!) and Maralen hidden in the 99, you can play straight control, or focus on Rogue combat damage with stuff like Conspiracy and Arcane Adaptation
Of course, we knew what would be the most expensive, but Ill bet you didnt have Jumpstart 2022 on your bingo card