Number 96: Dark Mist

Level 2 DARK/Fiend Xyz Effect
100 ATK / 1000 DEF

3 Level 2 monsters
Once per battle, during either player's turn, when an attack is declared involving this card and an opponent's monster: You can detach 1 Xyz Material from this card; halve the ATK of the opponent's monster, and if you do, this card gains that same amount of ATK.

Rulings – Yugipedia

Printings:

Order of Chaos: ORCS-EN043 (Ultimate Rare) - 2012-01-20
Order of Chaos: ORCS-EN043 (Ultra Rare) - 2012-01-20
Star Pack 2013: SP13-EN031 (Common) - 2013-03-01
Star Pack 2013: SP13-EN031 (Starfoil Rare) - 2013-03-01
Genesis Impact: GEIM-EN052 (Rare) - 2020-12-03

Prices:

Cardmarket: 0.03 €
TCGplayer: $ 0.18