When this card is destroyed by battle with an attacking monster your opponent controls and is sent to the Graveyard, you can equip this card to that monster. The equipped monster loses 1800 ATK. When it is destroyed and this card is sent to the Graveyard, you can Special Summon this card.
holyshit I was convinced it was level 4 until I read your comment
to get this to work, does this have to be in attack mode. i had it in defense mode, face down, my opponent had 1 serpent night dragon and one unused spell/trap card face down. when i attacked and this card was sent to the graveyard, nothing happened. only 1 card was in the spell/trap zone and there was no monster effect that made it so that this cards effect would be prevented.