Skyrim Sidelines- Rjorn's Drum and Halldir's Cairn: Worst Party Ever

If you've been working on the Bardic College quests in Solitude, you may have been sent down here to collect the legendary drum of Rjorn.  It's also possible that you were sent here from Falkreath by Runil, whose missing journal is liable to show up here if you haven't been into the dungeon previously.  Either way, the rewards for scouring this dungeon are high, and you may want to stop by even if you don't have either quest, particularly if you're a collector of rare weapons.

Halldir's Cairn can be found up a mountain to the West-Southwest of Falkreath.  Make sure you collect the mushrooms from the ground outside- they're a pretty good indicator of the major resource found here- mushrooms.  The other thing you'll find here in spades is ghosts, which makes for an interesting time.  If you're an up-and-at-'em melee monster, you'll mostly find the visuals intriguing, but sneakier characters will discover that it makes for a tense but rewarding delve.  This is primarily because a lot of the ghosts will be completely invisible to you until they become aware of you- even only slightly by a fumbled bit of sneaking or an attempt to creep past under their noses.  This can be great for your pickpocketing skill if you're extremely sneaky already, or it can just make things extra-interesting.

The dungeon opens with a tunnel leading into a large cavern.  The floor and ledges are positively covered in all variety of cave mushrooms, the sole exception being the glowing wall mushrooms.  There are also a couple of iron ore veins here for the miners and smiths (which should really be everybody, as the rewards for being able to craft and improve your own gear are immense).  The center of the room is dominated by a pile of blood-soaked rocks surrounded by corpses, bones, and a bright blue glow.

Agrius' Journal, a small book, can be found at the base of a small bookstand here as well- it details the adventures of Vidgrod, Raen, and Agrius, who were run out from a group of bandits and holed up in the cave.  Agrius' fellows fell to the curse here first, but he succumbed as well- the three of them threw themselves onto the cairn and died to supply the tomb beneath with protective ghosts and raw power.  The draugr Halldir is the source of this, and waits at the end of the cairn with the reward or rewards you seek.