The sparkling artwork, illustrated by Yashiro Nanako, gives true testament to this generations terastalization mechanic with Umbreon adorning that famous multi-colour crown, perched in front of a glowing harvest moon (and no, the Sunbreon name doesnt really make sense, does it?)
While it can be an attacker, you're much more likely to use Sylveon to improve your deck's consistency by drawing all the cards you could need
That scarcity was also reflected in the game's rules too
For example, if you sacrifice a nontoken Clue artifact, such as Candy Trail from the Wilds of Eldraine set, Piper Wright's last ability will trigger
While they read like niche color hate, the absurd efficiency of a one-mana counterspell/one-mana removal split card elevates this to an S+ sideboard card for red decks, and a mirror-beater for any blue deck capable of fetching Volcanic Island which is all of them