Kingdoms of Amalur: Reckoning - Pride Before the Fall

Make your to the SE corner of the Caeled Coast and talk to Agarth. After a short chat, Alyn Shir and Ventrinio will appear. You will gain a gift from Ventrinio that will protect you from Dren. You should save because you'll get two Persuasion checks here. Talk to him and you'll get your first persuasion chance early on.

Dren

After that, you will fight him but neither of you will take damage. Don't turn off safety mode to try to hurt him because you will incur a bounty for assault despite causing no damage.

After you fight for a moment, he'll talk to you again and you'll get your second persuasion opportunity. Immediately after, a fight will start so put some distance between the two of you. This time, it's for real. He can be aggressive with his sword and has a few spells but his melee combat is far worse than his magic. Keep your distance and play ranged, you shouldn't have a problem. Just watch out for when he teleports because he may end up behind you.

Honestly, I found avoiding his first attack to be the toughest part of the fight.

After you defeat him, Agarth will approach you and tell you to get into the House of Pride to remove the Tuatha there. You will have three allies but they can die. The first room isn't too difficult and is almost all soldiers. Take out the soldiers here and then make your way to the hallway to the NE. There will be a few guards patrolling this hallway and you should see if you can get them to come to you rather than chasing after them because there are a lot of Tuatha in that room including three Priests. It is definitely doable but it's going to cost you a lot of potions.

The next room will have a Bolgar and three Tuatha in it. One of the Tuatha will be an Overlord Priest but he operates just like any other priest. The soldiers shouldn't pose a threat but the Bolgar will have a shield and the Priest will be hurling spells. Moving around a LOT is important in this room. Stay out of reach of the Bolgar and the Priest and use ranged attacks when you can.

You'll enter a corner room and there will be on warded chest in this room. Head out of the room to the SW and you will meet a Knave of Pride. He will ask you to kill the Witch Knight Myrna. Make your way past him and you'll run right into here.

Myrna

Myrna is not a particularly difficult fight but you need to watch out. She has an attack that could kill me in a single hit (not sure what it was) and an Ice Mist that drains your health rather rapidly but isn't entirely obvious, particularly in the strange coloration of Fate Shift. However, most attacks will stun her so I would try to find something suitably fast that kept the stun on her. If you DO Fate Shift, watch for that Ice Mist and you should have no problem taking her out in that one Shift. She'll summon a Faer Grota but it isn't particularly important to this fight. Just make sure it doesn't sneak up on you and you should be fine.

After the fight, destroy the Chantry, loot the chest in the N offshoot of the round room and talk to the Knave again to finish this quest.