Kancolle Movie. BD/DVD will be out in roughly 3 months time.
Because,
Destroyed Counterdragons = Sunk shipgirls
Angolmois Core = The main body commanding the Abyssal Fleet (Which is the cause of the Abyssals coming out in that region
Heads of the Dragon Skull representing the dead counterdragons who wants revenge = Abyssal enemies
Shamash = Shipgirls