Mermail Abyssbalaen (MP14-EN055) [2014 Mega-Tins Mega Pack]

You can discard 4 other "Mermail" monsters to the Graveyard; Special Summon this card from your hand. When you do: Target cards your opponent controls, up to the number of "Mermail" monsters in your Graveyard (if possible); this card gains 500 ATK, and if it does, destroy those targets (if any). You can Tribute 1 other face-up Attack Position "Mermail" monster; this card gains the following effect this turn.
<br>• At the start of the Damage Step, if this card battles a Defense Position monster. Destroy that monster.