Skyrim Sidelines- Red Eagle's Sword: The Cairn of Rage

Having finished up in the Forsworn camp, head up the wooden stairs to the rent towers and open the iron door to the first one.  The first floor of this tower holds yet another copy of The Legend of Red Eagle, and the second has only a troll skull and a burial urn of interest, though it does also have the drawbridge and pullchain to lower it so that you can reach the other tower.  Use this to cross and immediately loot a chest in the far side of the same floor.

Use the ramp at the drawbridge to head down the second tower, snagging a soul gem and a large potion from a ruined table, then head further down for another high-value potion.  Unbar the iron door and open it to gain access to the top of the mountain, where several points of interest lay- your focus at the moment should be the Rebel's Cairn.

On stepping out of the tower, look to your right and locate the ruined tower on a crag in the distance.  This is in roughly the direction you want to head, though the Cairn is slightly to the left of that.

The Cairn itself is a cave under some very large rocks, marked by a brazier and a rockpile topped with a sword- and surrounded by a distressing amount of human remains.

The entrance tunnel to the cave is chock-full to the gills with mushroom patches.  It takes a bit of jumping around to get onto the ledges where some of them lurk, but it can be well worth the effort if you're at all in need of alchemical ingredients.  The round 'main cave' is similarly fungus-laden, though it also contains a dead adventurer with yet another copy of The Legend of Red Eagle and an iron ore vein.  More significantly, the outcropping over the pool at the center of the cave has a weapon stand, made to receive one particular sword- Red Eagle's Fury.