OK I am in the Dark Wraith Covenant now, so I can invade other players? What are the benefits of doing that? Just griefing?
Depends, you can join it to actually PvP (can only invade players same and above your level IIRC) or you can use it to grief, i.e make a pimped out low level character and grief new players because that's so much fun obviously
What does Offering Souls to the Lordvessel do?
When you get the souls of
the Four Kings, Gravelord Nito, Seath and the Bed of Chaos
the last area