This is the very beginning of the Rikantus/Nektropos Castle storyline, which continues all the way through the expansion, Chains of Eternity, where we see two of the Sisters from the Castle in Ethermere. We learn here that Rikantus is a trader of rare trinkets.
This content is heroic no matter which way you cut it. However, with mercs and careful body pulls, you can survive it solo, especially with a pet class. Otherwise, a small group will be needed.