Its enough to make you want to sell your cards in frustration
Like most Magic: The Gathering cards, the value of Unstable Frontier depends on a few consistent factors: its rarity, the printing and finish (regular or foil), its physical condition, and the set it was printed in (The List)
Even more impressive is her second ability which deals two damage to your opponent while healing two damage from you everytime you play a card with a cost of three or greater
Chocobo Bundle Next, Wizards of the Coast is releasing a Chocobo Bundle for the set
When the next restricted list announcement rolled around, a pretty unheard of number of cards were simultaneously added to the Vintage Restricted List: Crop Rotation Doomsday Dream Halls Enlightened Tutor Frantic Search Grim Monolith Hurkyls Recall Lotus Petal Mana Crypt Mana Vault Mind Over Matter Mox Diamond Mystical Tutor Tinker Vampiric Tutor Voltaic Key Yawgmoths Bargain Yawgmoths Will This list included most of my deck (every card but Force of Will, Defense Grid, and City of Brass would end up restricted at some point), as well as lots of other cards that were part of other broken decks that were feared to be the next to rise up
Other cards like Coiling Oracle or Sylvan Messenger may offer more immediate value, but Elvish Visionary's simplicity and efficiency make it a reliable choice that should see play in the right deck