There's no way of knowing if you'll find the most valuable Magic: The Gathering card until you start looking around, especially considering that at the end of the day
for now, however, why not check out the most valuable cards from Ursulas Return?
Sorcery Color tag templates(None) Unearth Return target creature card with mana value 3 or less from your graveyard to the battlefield
Overall, this card is a draw engine, and if you build around it, the strategy is perfectly playable, even if it's not to most players' taste, especially as playing cards exerted can be risky against more aggressive decks
Elsa The Fifth Spirit is a brilliant upsetter who can take out a troublesome character on her first turn and stay safe on the next
Ive also seen versions utilizing Bolt Superdog over Robin Hood Champion of Sherwood and have been very impressed with its performance and ability to win games quickly