Spellbane Sigil (Blue)

At the beginning of your action phase, destroy this.

Arcane Barrier X

Rulings

From the Omens of the Third Age release notes

Spellbane Sigil’s first ability triggers at the start of your action phase. When this triggered effect resolves, you will destroy Spellbane Sigil.
Spellbane Sigil’s second ability is an Arcane Barrier X. If you would be dealt arcane damage and you decide to apply Spellbane Sigil’s arcane barrier prevention effect, you must declare the value of X, where X is equal to the amount of resources you will pay and thus reduce the arcane damage event by that value.
You can declare the value of X = 0 when applying Spellbane Sigil’s Arcane Barrier. If you would be dealt damage and you would apply an Arcane Barrier 0 prevention effect to that damage event, the damage value of the event is not reduced.

Keyword notes

Arcane Barrier - is one of the most common ways to prevent arcane damage. If you would be dealt arcane damage you may pay X{r} instead to prevent X arcane damage that source will deal.

You can have multiple instances of arcane barrier.
You can only prevent one arcane damage per arcane barrier per source.
You can prevent arcane damage you do to yourself.
Players cannot respond to the prevention.
To fully prevent a card dealing 3 arcane damage, you would require 3 arcane barrier and 3 resources to prevent it. To fully prevent 3 Runechant tokens (3 instances of 1 damage). You would require 1 arcane barrier and 3 resources to prevent it.
Preventing arcane damage does not destroy the equipment with arcane barrier (unless otherwise specified).
Arcane barrier is a replacement effect. It does not use the chain. Players cannot respond to the prevention.
Each source of arcane barrier can replace damage 1 time per source. To fully prevent a card dealing 3 arcane damage, you would require arcane barrier 3 and 3 resources to prevent it. To fully prevent 3 Runechant tokens (3 instances of 1 damage). You would require arcane barrier 1 and 3 resources to prevent it.
If a card has Arcane Barrier 2, you must pay the full two resources even if it only prevents one damage. You cannot choose to pay one resource to prevent one damage.
You can have multiple instances of arcane barrier, for example Nullrune Hood, Nullrune Cloak, and Nullrune Gloves.
Arcane barrier can be used every time you would be dealt arcane damage. It’s not limited to once per turn.
Each instance of arcane barrier you control can be used 1 time only, each time a source would deal arcane damage to you. For example if a source would deal 5 arcane damage to you, and you control two cards with arcane barrier 1, you will in total be able to prevent 2 arcane damage this source would deal to you.
To fully prevent a card dealing 3 arcane damage, you would require 3 arcane barrier and 3 resources to prevent it. To fully prevent the arcane damage from 3 Runechant tokens (3 instances of 1 damage), you would require 1 arcane barrier and 3 resources to prevent it.
A equipment with arcane barrier does not move to the chain when arcane barrier is used.
You can prevent arcane damage you would deal to yourself.
Players cannot respond to the prevention. Arcane barrier is a replacement effect, not an activated or triggered ability.
To fully prevent a card dealing 3 arcane damage, you would require 3 arcane barrier and 3 resources to prevent it. To fully prevent 3 runechant tokens (3 instances of 1 damage from difference sources). You would require 1 arcane barrier and 3 resources to prevent it.