Flash - Advent: Shellman (Either Attack Step)
By sending Soul Core to your Trash, stack this from your hand onto your target spirit.
[LV1][LV2] (When Advents) Exhaust two opposing Spirits.
[LV2] (When Attacks) You can summon one "Shellman" Spirit card among this Spirit's pre-Advent cards. When you've done so, put two cores from the Void to this Spirit.