The Best Class Cards Classes are pretty evenly distributed over the color wheel, and you should be able to find one that works with almost any deck
But if you were to do that, Id just run Heliod or Rosie in the command zone instead
It taps for all of the mana, you can leave it untapped and forget about it when youre not using it and not have to take damage from it every turn, its like $10 from 4th Edition so you can actually have reasonable expectations of owning one- there are lots of reasons that more decks in EDH use Mana Vault than Crypt
This runs a bit counter to the reasons that I praised Mishras Bauble, with the relevant upside of the card being that it does at least pressure players to play aggressive decks
I simply didn't know how else to use the card
Final point of note is that Agent is an artifact which increases his potential synergies while not being an issue in regards increase susceptibility to removal as you don't overly care about the body once you have cast it