Note this event can be used any number of times on your turn and can also trigger when you destroy an enemy unit.
It’s important to remember that this event is only in the attack phase, so you can't combo with Into Darkness and you can’t use it during the movement phase.
Glinting Speed can help you maximize the 5 strength of Selundar. It’s very easy with this event in combination with several boosts on Selundar to get in to almost any target you want and then get out, hopefully to a position where you can keep supporting the rest of your army.
Thanks to this event sometimes you can play Selundar super aggressively, ready to place some offensive gates next turn or a second round of sneaky attacks on the opponent summoner.