You play an Illumineer, a magic user who pulls "glimmers" (reimagined versions of Disney and Pixar characters) into the world to collect lore for the Great Illuminary
The highest sale price we've seen is for a Gem Mint 9.5 graded copy, which sold via Heritage Auctions in March 2022 for $36,000 - and $20,000 is a very normal price for a copy of the card in a more ordinary state
Or, combine it with mana storage effects like Electro, Assaulting Battery and save it up for another turn
It can be much harder when you've confirmed receipt which is why we add the separate dialog prompting you to check authenticity etc
Promise of Loyalty represents the partys resolve to continue on after learning the true nature of the world and they pledge to end the cycle of Sins Rebirth
Anyhow, while they often screw these things up as they make them too strong initially, this mechanic seems to have gone the other route