[StarMann]

The following rules are not "official" insofar as they don't apply to playing Arcana as a whole. However these will be the rules during any tournament hosted by me. This will aim to clarify some of the rules and rulings and allow the games to flow without having to stop and call for a judge.

Deckbuilding:

The following rules are subject to change per each tournament with new stipulations being added for each tournament variation:

A deck must contain a minimum of 30 cards and a maximum of 60.
You may use up to 3 copies of the same card in your deck.
You may only run a single copy of a 3 * creature or relic ward.


HP:

Players lose 1 HP if a creature card they control in attack position is destroyed by battle.
Players lose 1 HP if they are attacked directly by a creature.
Players can lose or gain HP as stated as card effects.
Players start with 10 HP.

Turn Structure:

Each turn has a distinct structure of different "phases".

The turn begins on the Draw Phase, during this the player draws a card for turn.
There is then a Standby phase, this allows either player to activate set runes before the turn player can play cards.
Following this is Main phase 1, here the turn player may play cards from their hand following the normal rules.
Next is the Battle or Attack phase. The turn player can declare which creatures are attacking. Attacks can only be declared one at a time with the defending player being able to choose a blocker for each individual attack. There is no separate Block phase.
Following battle is Main phase 2 where the turn player may play additional cards.
Finally there is the end phase to allow for end of turn effects to trigger and allow players to chain effects to them.


Start of game:

Players draw 5 cards at the start of the game as their starting hand. This hand may be reshuffled back into the deck and a new 5 can be drawn once. This is commonly referred to as a "mulligan".
The first turn of the game begins on Main Phase 2.

Creatures:

Creature summons are divided into Normal and Special summons.
A player may only Normal summon once a turn. Playing 1 * creatures from hand face up or set (played in face down defence position); or tribute summoning a 2 or 3 * creature are Normal summons.
There are no limits to how many special summons a player can do on any given turn.
Special summoned creatures can only be played face up, however you may do so in attack or defence position.

Creatures on the field only have effects while they are face up. Face down creatures cannot use their effects unless first flipped up. A creature that does not have a flip effect cannot activate its effect if flipped face up by combat.
Creatures with manual effect triggers can only be used on your own turn and may only be triggered once per copy of the card. If the card is removed from the field and readded its effect can be used again in the same turn.
Creatures with triggered effects (usually denoted by the "when" or "if" terminology) trigger on either players turn so long as the conditions are met.
Creatures with constant effects (also referred to as an "aura") are always active so long as the creature remains face up on the field. The most prominent example of this being Emperor's phoenix.
Creatures with effects that can only occur once per game are once per copy of the card. Unlike once per turn effects, these effects are not reset if the card leaves the field for any reason.

Creatures have a minimum of 0 power and 0 toughness. Creatures are not destroyed if they hit 0 toughness unless stated as a card effect.

Creatures not on the field can only have stats and effects that are on the card. They do not retain any buffs or additional effects.

Combat:

Defence position creatures cannot destroy other creatures by battle.
If a creature with power attacks a creature of greater toughness in attack position, the attacking creature is destroyed. 
//To better understand things, power is the only relevant stat when attacking and toughness is the only relevant stat when defending. You only ever compare the attackers power with the defending creature's toughness.
Creatures may attack once a battle/attack phase unless otherwise stated.
A creatures battle position cannot be changed the turn it is summoned or after it has attacked in a turn.

A creature in defence position may "block" for another card that is targeted for an attack. This reduces the power of the attacking creature by the blocking creature's toughness. The attacking creature cannot be destroyed by a blocking creature. If a blocking creature's toughness is lower than the attacking power then it is destroyed and any "remaining" power carries forth. After a block is resolved, the original attack may be called off by the attacker.

Multiple creatures can be declared for a single attack and their powers are combined and compared to the defending creature's toughness. The order of attack is chosen by the attacker. The attacking creature's power is deducted from the toughness and if the defending creature's toughness remains greater than 0, the attacking creature is destroyed (only if the defending creature is in attack position) and it moves to the next in the chain.

If a rune is activated in response to an attack and does not cause creature destruction as an effect, the attack may be called off.

Runes:

Creature effects may be chained to the activation of runes so long as it is a valid trigger. You cannot manually activate a creature effect in response to a rune when it is not your turn.

Runes effects only trigger after the cost has been paid and resolved. If you are required to sacrifice a creature it must leave the field before the effect is on the chain. These will still trigger "on sacrifice" or "on HP loss" effects which can be chained off of before the rune's effect is on the chain.

The chain resolves backwards, from the latest effect towards the first. Effects are still on the chain even if the card that triggered it is destroyed further down the chain.

Runes are immediately sent to the netherworld once their effects are resolved and when they are destroyed.

Wards:

Wards can only be played from hand if there is no current chain.

Hand limit:

Any cards that are added to a full hand are immediately discarded.

Banlist:

There is currently no overarching ban list. However each individual tournament may impose its own restrictions, this will be stated in the forum post.

Erratas:

There are currently no card text changes.