It's a tiny ball, mind you, and not remotely a big deal, but when you're performing on the level that Wizards is, you're playing a game of inches
This appears to be the bonus card for the Whispers in Candlekeep drop, which puts the spotlight on Miirym, Sentinel Wyrm
This article follows the previous ones where I looked at the best cards from , and
#5 Lilly's Determination (FA) 150220 The full-art variant is more common than the SAR, but still a top card
On the other hand, there are some non-Niv decks in older formats that could probably use Jegantha, the Wellspring, the question is whether starting with a random 5/5 for five in hand is the best use of a sideboard slot