Sigil of Silphidae (Blue)

Go again

When this enters or leaves the arena, you may banish another aura from your graveyard. If you do, deal 1 arcane damage to target hero.

At the beginning of your action phase, destroy this.

Rulings

From the Compendium of Rathe release notes

Sigil of Silphidae first ability triggers when it enters the arena (e.g. resolves on the stack or when it is put into the arena from another card’s effect). It also triggers when it leaves the arena (e.g. when it is destroyed, when it is banished, etc.). This is an optional targeted effect: you must target a hero when you add the triggered effect to the stack; however, you choose whether or not to banish another aura from your graveyard when the triggered effect resolves. If you banish another aura from your graveyard this way, you will deal 1 arcane damage to that targeted hero.
With optional targeted effects like this one, you may choose not to target a hero when adding Sigil of Silphidae’s triggered effect to the stack. If you do not target a hero, none of the effects of banishing an aura or dealing damage are generated.
If Sigil of Silphidae triggers from leaving the aura, that Sigil of Silphidae cannot be chosen and banished from resolving its triggered effect.
Sigil of Silphidae’s first ability is not functional while it’s defending. It will not trigger this ability when it leaves the arena while it’s defending on the combat chain.
When resolving Sigil of Silphidae’s triggered effect, there is no priority between any of the effects generated by the card (e.g. banishing an aura card, dealing arcane damage).
Sigil of Silphidae’s third ability triggers at the beginning of your action phase. You will destroy it when this triggered effect resolves.

Keyword notes

Go again - Go again allows multiple actions to be played in a turn when usually playing an action with use up your action point, and therefore end your turn. A card with go again gives the controller of that card or activated ability 1 action point when it resolves.

When an action with go again resolves, its controller gains 1 action point.
Multiple instances of go again on the same card or activated ability do not stack. If a card or activated ability has multiple instances of go again when it resolves its controller gains 1 action point only.
If an action with go again does not resolve, its controller does not gain 1 action point.
You cannot reveal a card with no to Belittle. The card must have a value to its power that is 3 or less. (0 is a value)