Each time this card destroys 1 monster on your opponent's side of the field by battle and sends it to the Graveyard, this card gains 500 ATK.
Rulings
Individual Card FAQs
The effect of "Millennium Scorpion" is a Trigger Effect. Each time it destroys a monster on your opponent's side of the field and sends it to the Graveyard as a result of battle, it activates. This effect can be chained to. You can activate "Divine Wrath" against it.
If "Millennium Scorpion" attacks and destroys a Monster Token, the effect of "Millennium Scorpion" does not activate because a Monster Token isn't sent to the Graveyard.
If "Millennium Scorpion" has an ATK boost from its effect, but is removed from play with "Interdimensional Matter Transporter", or flipped face-down, the effect is reset and its ATK returns to normal.
EARTH|
Level 5|[ Insect / Effect ]
ATK 2000|
DEF 1800