Introduced in the very first Xenoblade Chronicles game, Unique Monsters are a staple of the series, represented as powerful monsters for players to try and take down for added challenge.
Advent Wolf Marduk is a Unique Monster that appears in Xenoblade Chronicles 3: Future Connected. It can be found in a cave in Vermillion Woods and defeating it counts towards completing your Enemypaedia.
Advent Wolf Marduk (Level 9) | Vermillion Woods
For assistance with finding all Unique Monsters in Vermillion Woods, why not check out our useful guide below:
[Guide] Vermillion Woods Unique Monsters | Xenoblade Chronicles 3: Future Redeemed