Flash - Grand Advent: Imaginary Beast & Cost 2/4/6/8 (Either Attack Step)
By either sending your Soul Core to the Trash, or putting a core from your Grandwalker Nexus to a spirit you control, stack this from your hand onto your target spirit.
[During Advent][LV1][LV2][LV3] (When Advents) During this turn, one opposing Spirit/Ultimate gets -10000 BP. Activate this effect an amount of times equal to the Cost of this Spirit's topmost pre-Advent card, and destroy every Spirit/Ultimate whose BP is brought to 0.
[LV3] (Your Attack Step) A total of 3 cores from opposing Spirits/Ultimates destroyed due to having 0 BP are sent to the Void, not the Reserve.