Elven Relics

It's not entirely clear which relics need to be captured. I assume it's a quiver and a bow. But what is the third relic? If it's the Sea Elf's Secant, I've already captured it, but the quest isn't being registered. I can't enter the dungeon. How do I kill the Dark Elf? I've killed the Wood Elves. It's unclear what to do next on the map.
It's unclear where the red key master is located. I retrieved the bow through the astral gate.