After going through the entryway shaft, Elden Ring fans will drop into a murky poisonous swamp.
Certain parts of the armor, such as capes, are usually removed.
If you want to farm for this item, head to the Saintsbridge Site of Grace in Limgrave, northeast of Stormgate, to find one patrolling the bridge nearby.
When this happens, head back to the Roundtable Hold and loot his corpse to get the Spellblade armor set without shattering your moral compass.
This list is ordered with the heaviest armor sets at the top and lightest at the bottom and should be pretty close to the exact order you see in your inventory.
Take it back to Sellen at Waypoint Ruins, and talk to her a few times until she gives you the Sellian Sealbreaker.