BOOOAL and the Kua Toa. Either having BOOOAL show up later on as we harvest more blood for him (Perhaps he gives us new shiny things to further the bloodshed) or the Kua Toa appear bringing gifts for their new god (As well as more scenes of bloody sacrifice)

The Shadow Druids. Okay, so 3 Shadow Druids appear... Then get promptly murdered and then... This sect never appears again in the game ever, despite their being 2 Druid companions and a Druid heavy ally faction?