Keystone - The Wounded Monk | Side quests Lords of the Fallen Guide

It is really worthwhile to help the monk.

After you exit the Citadel for the first time, you will see a gate ahead of you. After you use the levers on its both sides, you can talk to the Wounded Monk [M2,1]. He will ask you to cut his hand odd (you will receive the Butcher axe), and after you talk to him again, you will be able to give a potion to him (you lose one slot, but you obtain 500EXP).

You meet the monk later on, at the Citadel.

If you rendered help, on to the monk, you encounter him again, at the Citadel; after the conversation with the Captain walk ahead a bit, and enter the room on the left [M5,2]. Now, the Wounded Monk asks you to clear his works ([M2,21]), in the Southern Watchtower (you need to kill the Spider there, and let the monk know about it).

Bring the Tyrant Hearts to the workshop to increase the potency of your health potions.

The last part of the quest is to find the Tyrant Harts (four, at least). Take the items back to the monk's works, for which he upgrades your health potions (they replenish more health). After you bring all 12 hearts, the quest will be completed, you will receive the potions upgraded to a maximum and, additionally, 2000EXP.