Find Antanas and Kaslo at the Monastery Citadel | The Temple Lords of the Fallen Guide

After the battle, talk to Yetka, and then, to the Wounded Rhogar (do not kill him!). You can head towards the exit, over the stairs, to the room on Rhogar's left, and then up (the gates on the right lead to the caves that you have already been to. If not, go there to find an Ancient Tablet and open two chests).

The Tyrant is waiting at the top of the stairs. Get around him and enter the room quickly. Then, climb another stairs, where you find his heart.

Watch out for the Tyrant here and it is best if you get around him quickly. Head towards the stairs on the right side of the chamber. At the top, you will find a Crossbowman. Behind him, among urns, there is one with the Tyrant Heart inside. After you collect it, you can start the fight and cross the gate [M3.B] (open it by pulling the lever).

After you exit, talk to the Deserters.

Behind the door, you will find Deserters. While talking to them, you can give a health potion to one of them (decreases the maximum amount by 1, 500 EXP) and promise him that you help them clear the tower (this means the Western Antechamber). You are going there anyways so, you could take a look at that location (along your path, watch out for the Eternal Flame opponents). Inside the antechamber, you will have to defeat a Mutant, a Hell Hound and a Forger with a crossbow.

Inside the antechamber, there are several opponents.

After you have done that, return to the Deserters (you receive 500 EXP and the Defender dagger). Now, you can leave this location through the portal at the end of the Interdimensional bridge. Along your path, see the Blacksmith (2000 EXP, from now on, you will be capable of crafting runes at each anvil).

The wounded soldier suggests that you go to the Catacombs.

After you return to Keystone, you will meet a dying soldier (after his death, collect the Human Tattoo). Across the Cemetery, head towards the entrance to the Catacombs [M2.A]. It is located on its left. Along your path, you only need to watch out at the Cemetery - in front of the entrance, you will have to fight two quick Dwarves, and a Forger with a crossbow.

As soon as the Guard drives his sword into the ground, attack. Just make sure that he does not drive it into you, which results in your death.

It is not them that are the trouble, though - in front of the entrance, there also is a Guard, which is a bit weaker version of the First Warden , the boss. Also this time, watch out for the charges, sword blows and, especially for the deadly whirl towards the end of the battle, and the powerful sword swipe that can even kill you (the swing and raising the sword over the head).

The main entrance to the Catacombs.

After the fight, there is nothing more in your way so, enter the Catacombs.