Luminaris, Celestial Fury

Once per Turn Instant -

: Target angel attack or attack action card with Herald in its name gets go again.

Rulings

From the Dusk till Dawn release notes

Luminaris may target either an attack action card with Herald in its name or an angel attack. It does not have to target an angel attack with Herald in its name.
Luminaris may be activated during the resolution step of combat, after damage is dealt (damage step), but before the controlling player gains an action point from go again (link step).

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)