Skyrim Secondaries- Forbidden Legends: Threshhold of Endurance

Once the scourge is dead, check the area and you can turn up some gear and a few leather strips, then head onwards to the doorway on the third level of that room with the pillar in it.  Take care here- there's an obvious lever, but rather than dropping the drawbridges it prompts a quartet of spears to impale you.  Instead, walk up to the obvious lever and then turn right- a second lever is concealed by the rock formations against the wall.  This opens your path onwards to the ledge running around the pillar.  On the ledge you'll find another lever- but this is again a trap, if a trap of a different sort.

Across the second drawbridge wait a pair of draugr, who cannot get to you until the bridge is down.  Rather than welcoming them and their sharp weapons into your face, it's a much safer option to edge over to one side of the drawbridge and weaken or kill them with your arrows or ranged spells.

A third draugr waits over there off to the right, and clever use of arrows can lure it forwards- and right into the audible scything blade trap that guards that hallway.  Mind, the trap might not be triggered if you drop the drawbridge instead of attacking the draugr at range- the trigger panel for the pendula is behind the two draugr that watch the bridge.  This means that if you take them on in melee you may find yourself facing their third in a hall full of deadly swinging blades- not the best option- so be careful when you take that right turn if you skipped the opportunity for a ranged assault.

Ignore the stairs down here (they're blocked) before heading past the swinging blade trap, preferably using it to take out the third draugr on this side of the drawbridge.

The far end of the danger hall includes a pull-chain that will turn off the swinging blades, so use that to keep yourself a bit safer, then head down the stairs.  There's nothing of real value on the shelves here so keep going up the other stairs and into the wide tunnel.

This tunnel leads you into the tomb of Sigdis, where the second Gauldurson brother waits to give you another tough fight.

The chamber of Sigdis' tomb is strange- in addition to the small standing area next to the dead end you already looked in here from, there are two other circular platforms with ramps up to them in the waterlogged area.  Sigdis himself first appears from his sarcophagus on the far platform, and only emerges once he is aware of you- which means that sneaky characters can get quite close and they, as well as those who charge in at high speed, can actually do some nice damage before starting the fight itself.