Every ruling,
cited.
Arbiters Grimoire answers a Magic rules question the way a judge does: it reads the official Comprehensive Rules first, then gives you the verdict, the reasoning, and the rule numbers it stood on.
Every citation is a chip you can open. Nothing is recalled from memory.
7-day free trial on every new account · $5/month after · no card to start
Because your creature has deathtouch, any nonzero amount of damage is lethal damage for the purpose of assigning combat damage 702.2c. Trample lets you assign the rest to the defending player 702.19b.
- 1Assign 1 damage to the 2/2 blocker — lethal, given deathtouch.
- 2Assign the remaining 4 damage to the defending player.
- 3The blocker is destroyed as a state-based action once damage resolves.
The rulebook is read first
Every question searches the parsed Comprehensive Rules and hands the matching passages to the model before a word of the answer is written.
Every chip opens its rule
Rule numbers appear inline and in a Rules Cited strip. Click one and the rule text opens beside the ruling, so you can read the source yourself.
Cards are looked up live
Name a card and the Arbiter pulls its current Oracle text from Scryfall rather than reciting a printing it half-remembers.
A judge for the table you actually play at
Describe the board state in your own words, pick the format the ruling should be made under, and send. You get a one-line verdict, the reasoning underneath it, and the rules it rests on.
Format-aware. The same board reads differently in Commander and in Pauper — the ruling knows which you asked about.
Card text on hover. Any card named in an answer opens its mana cost, type line, and Oracle text without leaving the thread.
Kept in the archive. Rulings are saved and grouped by day, so the argument you settled last week is still there next week.
Brew with the rules lawyer already at the table
Put the list on the right, say what the deck is trying to do on the left. The builder answers with what to add, what to cut, and the reason for each — checked against the format you chose.
Legality is enforced, not assumed. Duplicates, banned cards, and names it doesn't recognise are flagged before the question is even sent.
Commander-aware. Pick a legendary creature and the slot rules, the 100-card target, and the ban list follow.
Decks are saved with their conversation. Reopen one and the build session picks up where it stopped.
Three moves, in the order you'd make them
Bring the list you already have
Import a CSV straight out of ManaBox, Moxfield, Archidekt, or Deckbox. Columns are matched by name, duplicate printings merge into one line with a summed count, and the file is parsed in memory and discarded — it is never written to disk.
Let it check itself
The list validates as you type, against the format you picked. Banned cards are off by default — the builder will never recommend one unless you deliberately allow it.
Then argue about it
Say what the deck wants to do and it answers in adds, cuts, and reasons — the same cited voice as the Arbiter, pointed at your curve instead of your combat step.
You describe the board
Plain language, whatever detail you have, under the format you're playing.
The rulebook is searched
The most relevant Comprehensive Rules passages are retrieved and handed over as evidence, with card text pulled in when you name one.
You get a verdict and its sources
One line of answer, the reasoning beneath it, and every rule number it used — openable, so you can check.
Five dollars for the door. Credits for the work.
The subscription keeps your account open. Credits pay for the AI's actual usage and are deducted as you go, so a quiet month costs you almost nothing.
Access to the Arbiter, the Deck Builder, the searchable rulebook, and your saved archive. Cancel any time — you keep what you've already paid for until the period ends.
Enough for many game nights. Start here, see what you actually spend, and top up only if you run dry.
For the player who is asked to settle everyone else’s arguments, and rebuilds two decks a week.
The ceiling. An account holds at most $20 at once, so this fills an empty balance in a single purchase.
Credits are non-refundable and an account can hold at most $20 at a time. Your first purchase seeds a monthly spend limit from your balance; you can tighten it whenever you like on the account page.
Settle it properly.
Make an account, ask the question that's been dividing your pod, and read the rule it comes from.