Stalblind is the boss of the Thieves' Hideout, a large skeletal knight. This battle requires clever use of your merge ability. In the first phase, Stalblind will charge at you with its sword and shield. Its shield is impenetrable from the front. The trick is to merge into the wall behind Stalblind. When it charges past, quickly emerge from the wall and strike its back with your sword.
After taking enough damage, Stalblind will shed its armor and become a floating skull. It will then summon other skeletal enemies. Defeat these smaller enemies first. Stalblind will also try to suck you in with a powerful vacuum attack. When it does this, merge into the wall to avoid being pulled in. After the vacuum attack, it will be vulnerable for a short period. Continue to strike its skull until it is defeated, rescuing Gulley and obtaining the first Lorule Sage.