Knowledge Pool is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.
Official card text
Imprint — When this artifact enters, each player exiles the top three cards of their library. Whenever a player casts a spell from their hand, that player exiles it. If the player does, they may cast a spell from among other cards exiled with this artifact without paying its mana cost.
Complete guide
Knowledge Pool is a complex artifact that turns the game into a chaotic exchange of spells. When this artifact is on the battlefield, the spells you cast from your hand serve as a currency to purchase other spells already tucked away in the pool. It completely changes the flow of resources, forcing players to think several steps ahead to claim the best spells.
What Knowledge Pool Does
Knowledge Pool has an Imprint ability that exiles the top three cards of every player's library when it enters the battlefield. Its second ability creates a replacement-style effect for spells cast from the hand. Instead of the spell resolving normally, it is exiled into the pool, and the caster gets to pick a different nonland card already sitting in the pool to cast for free. This includes cards exiled by the initial Imprint ability or cards exiled by previous spell casts.
Resolving the Trigger Step by Step
First, a player casts a spell from their hand. This puts the Knowledge Pool trigger on top of that spell on the stack. When the trigger resolves, the original spell is exiled. If and only if that spell is successfully exiled, the player may choose another nonland card currently exiled by that specific Knowledge Pool. They then cast that chosen card without paying its mana cost. Because this happens during the resolution of an ability, timing restrictions based on card type (like Sorceries or Creatures) are ignored, though specific restrictions like 'Cast only during combat' still apply.
Common Mistakes and Clarifications
A common point of confusion is what happens if the original spell is countered before Knowledge Pool resolves. If the spell is no longer on the stack to be exiled, the player does not get to cast a spell from the pool. Additionally, if you cast a spell with X in its mana cost from the pool, X must be 0. Remember that you are still 'casting' the second spell, so other 'whenever you cast' abilities will trigger for the new spell as well.
When to Play Knowledge Pool
Knowledge Pool is best played when you can benefit from casting multiple spells or when you want to lock down the board. Since it forces players to cast spells from the pool, it can be combined with effects that prevent players from casting more than one spell per turn, effectively stopping opponents from resolving anything at all. It is also excellent in decks that can generate value from 'on-cast' triggers.
Interaction examples
Gilded LotusYou have a Gilded Lotus already exiled by Knowledge Pool's Imprint ability. You cast a simple spell from your hand. Knowledge Pool triggers, exiles your hand-cast spell, and allows you to cast the Gilded Lotus from exile for free. The Gilded Lotus then enters the battlefield, ready to be tapped for mana.
Vanquisher's BannerYou have Vanquisher's Banner on the battlefield with 'Elf' chosen. You cast an Elf spell from your hand. Two things happen: Knowledge Pool triggers and the Banner triggers. You draw a card from the Banner first. Then, Knowledge Pool exiles your Elf spell. You choose a different Elf spell previously exiled in the Pool and cast it. The Vanquisher's Banner triggers a second time because you 'cast' a creature spell of the chosen type from the pool, allowing you to draw another card.
Guide written with AI from the official text and rulings. Official English text prevails.
How it works : Knowledge Pool
Original English text — Wizards of the Coast / Scryfall
- #1· Wizards of the Coast
You may cast any other card exiled by Knowledge Pool, including one owned by an opponent. Any card exiled by Knowledge Pool's "enters" ability or its other triggered ability may be cast.
No other card is named in this ruling.
- #2· Wizards of the Coast
The spell a player casts from their hand won't resolve if it's exiled, even if that spell can't be countered by spells or abilities.
No other card is named in this ruling.
- #3· Wizards of the Coast
If the original spell isn't exiled (perhaps because it's countered by another spell or ability before Knowledge Pool's second triggered ability resolves), the rest of the ability does nothing. The player doesn't get to cast an exiled card.
No other card is named in this ruling.
- #4· Wizards of the Coast
If there are no nonland cards exiled by Knowledge Pool, the original spell is still exiled.
No other card is named in this ruling.
- #5· Wizards of the Coast
You may pay additional costs, such as kicker costs, of the exiled card.
No other card is named in this ruling.
- #6· Wizards of the Coast
If the card has any mandatory additional costs, as Kuldotha Rebirth does, you must pay them in order to cast the spell.
No other card is named in this ruling.
- #7· Wizards of the Coast
Timing restrictions based on the card's type are ignored. For example, you can cast an exiled creature card this way. Other restrictions, such as Spinal Embrace's "Cast Spinal Embrace only during combat" are not ignored.
No other card is named in this ruling.
- #8· Wizards of the Coast
If the card you cast without paying its mana cost has an X in its mana cost, you must choose 0 as its value.
No other card is named in this ruling.
- #9· Wizards of the Coast
Any other abilities that trigger when you cast the original spell (for example, if you cast Emrakul, the Aeons Torn) will still trigger and go on the stack.
No other card is named in this ruling.
- #10· Wizards of the Coast
If multiple Knowledge Pools are on the battlefield, keep track of which cards are exiled by each of them. Whenever a player casts a spell from their hand: -- If all Knowledge Pools are controlled by the same player, that player chooses the order in which the triggered abilities are put onto the stack. The last one put onto the stack will be the first to resolve. -- If multiple players each control one or more Knowledge Pools, the active player put their triggered abilities on the stack in any order, then each other player in turn order does the same. The last ability put onto the stack this way will be the first to resolve. -- The first triggered ability to resolve will exile the original spell, then the player who cast that spell may cast one of the nonland cards exiled by the Knowledge Pool that generated that triggered ability. The abilities of other Knowledge Pools will do nothing when they resolve, as the original spell will already have been exiled.
No other card is named in this ruling.
Popular combos
Real combos played by the community, sorted by popularity.
Drannith Magistrate + Knowledge Pool
- 1Whenever a player casts a spell from their hand, Knowledge Pool triggers, exiling the spell and allowing the player to cast another card exiled by Knowledge Pool without paying its mana cost.
- 2Drannith Magistrate prevents opponent from casting anywhere other than their hands.
Lavinia, Azorius Renegade + Knowledge Pool
- 1Whenever a player casts a spell from their hand, Knowledge Pool triggers, exiling that spell and allowing them to cast a spell exiled by it without paying its mana cost.
- 2When an opponent casts a spell this way, Lavinia triggers, countering that spell.
Teferi, Time Raveler + Knowledge Pool
- 1Because of Teferi, opponent can only cast spells whenever they could cast a sorcery.
- 2Whenever they cast a spell from their hand, Knowledge Pool triggers, exiling that spell.
- 3The opponent cannot cast the spell as permitted by Knowledge Pool due to Teferi.
Archon of Emeria + Knowledge Pool
- 1Whenever a player casts a spell from their hand, Knowledge Pool triggers, exiling that spell.
- 2Because Archon of Emeria prevents players from casting more than one spell each turn, players cannot cast the spell permitted by Knowledge Pool, or any other spell that turn.
Knowledge Pool + Rule of Law
- 1Whenever a player casts a spell from their hand, Knowledge Pool triggers, exiling that spell.
- 2Because Rule of Law prevents players from casting more than one spell each turn, players cannot cast the spell permitted by Knowledge Pool, or any other spell that turn
Deafening Silence + Knowledge Pool
- 1Whenever a player casts a noncreature spell from their hand, Knowledge Pool triggers, exiling that spell.
- 2Because Deafening Silence prevents players from casting more than one noncreature spell each turn, players cannot cast a noncreature spell permitted by Knowledge Pool, or any other noncreature spell that turn.
Knowledge Pool + Eidolon of Rhetoric
- 1Whenever a player casts a spell from their hand, Knowledge Pool triggers, exiling that spell.
- 2Because Eidolon of Rhetoric prevents players from casting more than one spell each turn, players cannot cast the spell permitted by Knowledge Pool, or any other spell that turn
Vexing Bauble + Knowledge Pool
- 1Whenever a player casts a spell from their hand, Knowledge Pool triggers, exiling the spell and allowing the player to cast another card exiled by Knowledge Pool without paying its mana cost.
- 2If the player chooses to cast a spell, Vexing Bauble triggers, countering that spell since no mana was spent to cast it.
Legal formats
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Meta decks with Knowledge Pool
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