You can only activate 1 "Tenacity of the Monarchs" per turn
Since Bunnelby can attack twice in a turn, it can use Evolution twice, which means that its possible to evolve, say, an Oddish into a Vileplume [Ancient Origins], or Duskull into Dusknoir [Vivid Voltage], depending on which hurts the opponent more
Clocking in at 188 cards also makes it smaller than many of Scarlet and Violet's expansions
While Prismatic Evolution's prices are still far from stabilizing, it seems clear that Sylveon is staking a strong claim as the set's second most valuable Eeveelution behind Umbreon
I would be completely fine mixing this with regular cards in a proxies allowed game
For players wanting a competitive edge and collectors seeking a sleek design, this card delivers both