The rules, settled here

What a legal deck is

Main deck

40 cards

Rune deck

12 runes, shuffled separately

Copies of one name

3

Champion Legend

1

Chosen Champion

1 champion unit

Signature cards

3 in total

Battlefields brought

3, no two alike

Sideboard

10 or fewer, best of three only

• The three copies of a name include your Chosen Champion, so a deck running it may hold two more of that card and no more. Two cards that share a character but not a name are different names and get three each.
• Your Chosen Champion must be a champion unit whose champion tag matches your Legend, it starts the game in the Champion zone, and a signature unit can never be the one you choose.
• The three signature cards are a total, not three per name, and every one of them must carry your Legend’s champion tag. Signature cards cannot go in the Champion zone.
• You bring 3 battlefields and no two may share a name. Only one of yours ends up in play.
• A sideboard is a best-of-three thing. Cards swap one for one with main deck cards between games, and it may not be used at all in game one.

Setting up, and the mulligan

• Put your Champion Legend in the Legend zone and your Chosen Champion in the Champion zone, both face up.
• Set your 3 battlefields aside.
• Decide who goes first by any fair random method everybody agrees on.
• Shuffle your main deck and your rune deck separately, and keep them separate all game.
• Draw 4 cards.
• Mulligan once, in turn order: set aside up to 2 cards, draw that many replacements, and only then recycle the ones you set aside to the bottom of your deck.
• Reveal the battlefield each of you is using. In a single game it is chosen at random from your three; in a best of three you pick.

• Two battlefields end up on the table in a two-player game, one from each player, out of the 3 each of you brought.
• In a best of three, once a game has a winner, both battlefields that were in play are out for the rest of the match, so each player picks a fresh one for the next game. If nobody won the game, the same battlefields can be used again.
• Nobody channels a rune during setup. Runes arrive on your own turn, in the Channel phase.
• In a two-player game the player going second channels 3 runes in their first Channel phase instead of 2. That is the only first-turn adjustment: nobody skips a draw.

The board: where a card can be

Two groups. Board zones are where units and runes physically stand, meaning your base and the battlefields. Everything else is a non-board zone.

• Base. Your home location, one each. Units and gear arrive here unless something says otherwise, and channelled runes sit here. Nobody may ever move into an opponent’s base.
• Battlefields. The locations in the middle. A two-player game uses exactly two, one from each player.
• Facedown zone. One slot attached to each battlefield, holding the one card put there by Hidden. Only the battlefield’s controller may place a card there, and losing the battlefield removes it.
• Legend zone. Your Champion Legend sits here all game. It never enters play and cannot be moved or removed.
• Champion zone. Your Chosen Champion starts here face up and is played straight out of it. Once it leaves, it does not come back by normal means.
• Hand. Private. The Core Rules set no maximum hand size, and the Ending phase contains no discard step.
• Main deck and rune deck. Shuffled separately at setup, kept separate for the whole game, and both have a bottom that recycling sends cards to.
• Trash. Public and unordered. Killed permanents, spells that finished resolving, discarded cards.
• Banishment. Public, and much harder to come back from than the trash.
• Rune pool. Where energy and power sit between being added and being spent. It is emptied twice a turn and anything left in it is lost.
• The chain. A zone that exists only while something is being played.

Reading a card

• Top-left corner: the cost. The numeral is the energy cost. The symbols stacked beneath it are the power cost, one symbol per power. Plenty of cards have no power symbols at all.
• The name. A card with a subtitle is named "Short Name, Subtitle" for every rules and deckbuilding purpose, so two subtitles of the same character are two different cards and you may run three of each.
• The type line. Supertypes such as Champion and Signature come before the type. Tags such as Jinx or Equipment come after it and mean nothing on their own beyond what other cards say about them.
• Might. A unit’s single combat number. It is both what the unit contributes to damage and what it takes to kill it.
• Domain symbols, lower right. One or more of six.
• Reminder text is italic and in brackets. It is a summary, never a rule: its presence, absence or exact wording changes nothing. Flavour text conveys nothing at all.

The six domains, and your identity

Fury is red, Calm green, Mind blue, Body orange, Chaos purple, Order yellow. A card belongs to one or more of them, and the symbols in its lower right corner are what it belongs to.

The domains of your Champion Legend are your deck’s Domain Identity. A single-domain card is legal if that domain is in your identity. A multi-domain card is legal only if your identity contains all of its domains. Your rune deck follows the same identity.

Two symbols get their own shorthand in card text. The rainbow symbol means power of any domain, and a card that asks for power of its own domain accepts any one of the domains printed on it.

Paying a cost: energy is not power

• Energy is the numeral. Exhaust that many runes, turning them sideways. Any domains at all.
• Power is the symbols. Recycle that many runes of the matching domain, putting them on the bottom of your rune deck.
• Both land in your rune pool, and the pool is emptied twice a turn. Anything unspent is simply lost.

The turn, phase by phase

• Awaken. Ready every game object you control that can be readied.
• Beginning. Start-of-turn effects first, then the scoring step: you hold every battlefield you control, 1 point each.
• Channel. Put the top 2 runes of your rune deck into play, ready. Fewer than 2 left means you channel as many as you can.
• Draw. Draw 1 card. In a two-player game the first player draws on turn one as well.
• Main. Every rune pool empties first. After that the phase has no structure at all: play cards, activate abilities and move units in any order, as often as you can pay. Showdowns and combats happen inside this phase.
• Ending. End-of-turn effects, then all units heal, all "this turn" effects expire together, and every rune pool empties again.

Priority, focus and the chain

The chain exists whenever a card or ability is being played, and only one chain exists at a time. What you may do is decided by two independent switches.

• Open or closed. A chain exists, so the turn is closed; no chain, so it is open. In a closed state only Reaction may be played.
• Neutral or showdown. A showdown or combat is in progress, so the turn is in a showdown state; otherwise it is neutral. In a showdown state only Action or Reaction may be played.

Priority is the exclusive right to act, and one player has it at a time. Focus is the showdown version of the same thing: the attacker gains it as combat opens, and it passes when a chain empties during the showdown. Gaining focus gives you priority too, and passing priority does not cost you focus.

By default a card is playable only while you hold priority, on your own turn, in a neutral open state. The chain resolves last in, first out, which is why an answer resolves before the thing it answered.

Moving units, and what a showdown is

• Moving is a game action, not a chain item. It is instantaneous and cannot be reacted to.
• The standard move costs exhausting the unit: base to a battlefield, or a battlefield back to base. Ganking adds battlefield to battlefield.
• Several units may move in one action if they share a destination. Their origins may differ, and their exhaust costs are paid together.
• A standard move is available only during your own Main phase, in an open state, and never during a showdown or combat.
• Moving into a battlefield you do not control marks it contested, and a showdown is staged in the cleanup that follows.

Walking into a battlefield where no opposing units stand is a non-combat showdown. Both players still get their window, both may play Action and Reaction cards until everyone passes, and if one player’s units are the only ones left, that player takes the battlefield.

Combat, in three steps

Combat happens when units controlled by two opposing players are at the same battlefield. It only ever involves two players.

• The combat showdown step. The attacker is the player whose units applied contested; the defender is the other one, and units at that battlefield take the matching designation. The attacker gains focus. Triggers join the combat chain attacker first and defender last. Then the showdown runs until everybody passes.
• The combat damage step. Sum each side’s current Might. Starting with the attacker, each player assigns damage equal to their own total among the opposing units. Assigning is not dealing: when assignment is finished, all of it is dealt at once.
• The resolution step. Damage is dealt, then the combat cleanup heals every surviving unit and recalls surviving attackers to base if any defender is still standing. Only then is the result determined and control established. Combat ends and every "this combat" effect expires together.

Assigning damage: exactly lethal, then move on

• Lethal damage is non-zero damage equal to or greater than a unit’s current Might, counting damage already marked on it.
• You must assign lethal damage to one unit in full before assigning any to the next.
• You may not assign a unit more than the minimum lethal amount unless there are no other units left to assign to.
• Tank must be assigned lethal before any of its controller’s non-Tank units. Backline must be assigned lethal after them. Within each group the rule above still governs.
• If two units demand the same priority you choose the order between them, and if one unit somehow has both Tank and Backline you pick which requirement to satisfy.
• A unit that simply cannot be dealt damage is skipped, because no amount counts as lethal on it.
• A stunned unit contributes no Might to the damage step but still needs its full Might in damage to die.

Scoring, and the rule on the last point

• Conquer. You gain control of a battlefield you have not yet scored this turn: 1 point.
• Hold. You keep control of a battlefield through your Beginning phase, having not yet scored it this turn: 1 point.
• Either way, each battlefield can be scored only once per turn per player.
• Points also come from card effects that say so, and from an opponent burning out.
• The victory score is 8 by default, and a card or a game mode can change it. You win in a cleanup, once you have at least the victory score and more points than any opponent.

In practice the restriction starts to bite at 7 points. From there a conquer either takes the last battlefield you had not scored this turn, or it hands you a card and nothing else.

Burning out is not the loss condition new players expect. Draw from an empty main deck and you recycle your whole trash into it, randomised, choose an opponent to gain a point, and then finish the draw you were making. In the Draw phase that means you burn out and still draw your card. With an empty trash it simply repeats, handing out a point each time.

Where the official rules live

Riot publishes a rules hub carrying the Core Rules and the Tournament Rules as PDFs, plus per-set clarifications and errata. The Core Rules govern how the game works. The Tournament Rules govern deck registration, sideboards and event conduct, and they tighten some Core Rules numbers for competitive play.

If a ruling matters to you, read the numbered rule in the PDF rather than a summary of it, including this one. Every rule number cited on this page is from those documents so that you can.