Kill the Sanguine Noble boss

To complete this square you need to defeat Sanguine Noble, the boss underground the Writheblood Ruins. Wait until the "ENEMY DEFEATED" or equivalent screen appears to mark the square.

This square has synergy with Kill 3 Ruins bosses. It also has geographic synergy with Invade and Defeat Magnus the Beast Claw, as the invasion sign is also in the Writheblood Ruins.

Sanguine Noble counts as an Altus Plateau/Mt. Gelmir boss.