This short side-quest can be found in the Cemetery where we fought the Worshipper earlier. Clear the area of enemies and once it is safe, look for a hole in the ground beneath a large tree (almost directly opposite the gate to the demon realm portal). You can interact with the hole.

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Grab the Cursed Sword from the Old Quarters in the Citadel (left). Place the sword into the hole in the Graveyard (right) to fight a ghost for a reward.

If you have the Cursed Sword (which we can find in the Old Quarters section of Keystone Citadel) you will gain the option to bury it. Doing so will summon a spirit which will attack you and you’ll need to dispatch it.

Killing the spirit will earn Harkyn 1,500XP , an upgraded version of the Sword (Sword - Cursed Sword) and an achievement/trophy ‘I Feel Lucky’ .