To access the Abrassar Legacy Chest, you will need to enter a dungeon known as ‘The Slide’. This dungeon has four entrances. The entrance you need to use first is located north west of the Parched Shipwrecks, as shown below.
Note: To reach this Legacy Chest you will need to defeat a Shell Horror. It is therefore advised that you stock up on Poison Antidotes to avoid being killed by the Extreme Poison debuff. Alternatively you can consume Fungal Cleanser or Grilled Marshmelon to cure the poison.
Once inside, turn left (south east) and go up the slope. At the top you will find a Rock Mantis. Although coloured differently, it is similar to other Rock Mantis mobs, but with slightly more health. Once it’s dead, take the Old Levant Key from the skeleton on the ground. You can make use of this later on. Now go back to the main chamber where you entered The Slide. This time, turn right (north) and follow the tunnel path until you approach two iron gates.
Interact with the gates to open them. Between the gates you will see a lever, pull this to drain the water from the rest of the dungeon so that you can go back later and explore if you wish. Now continue west through the gates. In this room you will find two regular bandits which can be dealt with easily. After killing them, you will notice that the Legacy Chest is locked behind an iron gate to the south. To open the gate, first head north west and pull the lever beside the stairs heading down to the north.
Pulling this lever will open the gate at the bottom of the stairs, beyond which you will encounter a Shell Horror after interacting with the gate facing east. Shell Horrors can be difficult to deal with if you don’t have appropriate equipment. A high impact weapon is extremely useful here; the more you can knock the mob down, the less chance it will have to hit you. Kiting won’t necessarily work, as the Shell Horror regains 2.5 health per second. It deals both Physical and Decay damage, so be sure to use any armour or buffs which provide resistances. In addition, they can inflict the debuff ‘Extreme Poison’, dealing 3 Decay damage per second until cured. It is vulnerable to Lightning damage, so use this whenever possible. Your best chance is chaining as many attacks as possible which inflict both high damage and high impact.
When the Shell Horror is dead, you will be able to use the lever in the room from which it came. You will find it behind the pillar in the centre of the room. Once pulled, the gate to the south west will open, providing access to another lever. Pull this lever to open the iron gate where the Legacy Chest is located. You will now be able to use it and place any eligible item within the chest, ready to be inherited by a new character.
Note: You will need to follow these steps again with your new character in order to open the gate to the Legacy Chest. If you do this with a much weaker new character, you can avoid having to fight the Shell Horror by simply running around it and using the levers. You will then be able to run back to the Legacy Chest and open it to obtain the item.