If you activate Knowledge Vault's second ability, all that happens at that time is that you pay a cost of {0}. As the ability resolves, you must sacrifice Knowledge Vault. This is mandatory. If you are able to do so, you discard your hand and put all cards exiled with Knowledge Vault into their owners' hands. If you aren't able to do so because Knowledge Vault left the battlefield or changed controllers before the ability resolves, nothing happens.
You don't get to look at the cards exiled with Knowledge Vault.
You can activate the second ability any time you have priority, including in response to itself. However, you will only be able to sacrifice the Vault as the first such ability resolves.
Last observed on Scryfall 2 months ago at $47.70. Over the trailing 90 days the price moved between $35.16 and $47.70 across 51 observations. Cross-checked across TCGplayer, eBay sold, Cardmarket EU, and Star City.
This printing is one of 2 catalogued treatments from LEG — the lineup includes Nonfoil alongside the standard finish. Across our catalog the Rarix library tracks every variant in the same family so collectors can compare price, scarcity and demand inside a single lineage.
Card #281 of *Legends*, the set that shipped alongside the June 1994 Legends release.
Card type: Artifact, printed at rare. Rares occupy the bottom-of-pack rare slot in standard boosters. Mana cost: {4} (4 converted).
Legal in Legacy, Vintage, and Commander. This printing is on Wizards of the Coast's Reserved List — Wizards has committed never to reprint cards on that list, which underwrites a structural scarcity floor on every surviving copy.
EDHrec ranks this card #29,128 in Commander, putting it in the fringe-play tier of the format's playable pool.
Illustrated by Amy Weber. Rarix catalogs 367 other cards credited to this artist.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Amy Weber
Card data via Scryfall. Rarix is fan-made; not endorsed by the rights holders.
