You'll find the Rot Knight at the bottom of an area called the Sarcophagus Rift, which you can access by descending through the rift. However, before you can fight this boss, you need to have completed the main story first, at least as far as Shadow Keep.

When you reach the keep, a message will pop up saying "Somewhere, a great rune has been broken... and a powerful amulet." You can't reach the rift until then.

You'll be brought to the rift by completing Thiollier's quest. If you do this, you can also summon Thiollier to fight alongside you, although this is not mandatory to enter the fight. You can enter the fight regardless of whether you've completed his quest or not. Once you reach the Sarcophagus Rift area, continue down until you find the Place of Grace deep within the rift. Move forward and jump off the giant head to reach the arena.

In general, the Rot Knight fight isn't a fun experience for melee builds, as the boss moves around the arena a lot, leaving you with only a short window of time to land a hit or two. Ranged abilities, from magic to spells, work well against this enemy.

Like other enemies in the Elden Ring DLC, the Rot Knight is weak to Holy damage. They'll take a ton of damage from attacks based on this attribute, which is great if you're running a Faith build. It's also a good thing that the Rot Knight is also prone to bleeding if you're not, so bleeding out is also a good secondary strategy. While this boss isn't immune to fire damage, it's not as effective against enemies in the base game.

The Rot Knight's attack animations are long -- but with a delay -- and require some practice to get the timing right. You'll have little room to fire up flasks or recast buffs. The Rot Knight's gear has several tools to prevent you from doing this, forcing you to choose between getting hit and healing yourself, or escaping their offensive moves but staying one hit away from dying.

While the fight isn't explicitly divided into two phases, we've done so to make the information below easier to digest. Phase one covers all of the boss's main moves. Once you've learned to survive phase one, phase two is a breeze.

All of the moves we detail below are repeated throughout the fight. Knowing how to avoid them and when to strike back is essential to defeating this boss.

The Rot Knight can start the fight in two ways. They can either jump on you and slam into your position with their giant cleaver, or ride towards you on it and perform several swing attacks - this is more common when you're using a skill, as they're charging towards you. The former is usually followed by one of the Rot Knight's signature moves, the spin attack combined with the horse.

The combo attack begins with the Rot Knight jumping off his horse and performing three spins. Once this move is complete, he'll perform another three spins and charge attacks with his horse, and then repeat the moves. In total, you need to dodge three spinning sequences and two charges. To dodge the first spinning sequence simply roll towards them. However, when the Decay Knights attack with their horses, you need to roll towards the horses and quickly roll to the other side.

Defeating the Decay Knights will reward you with the Memories of Decay and 220,000 Elden Ring Runes.