Underdark Encounters: The Umber Hills

For the past year I ran a D&D 5e game set in the Underdark, or at least my version of it that featured elements from Hot Spring Island sprinkled in. The players all played Underdark races and never once saw the sun (the one they saw when transported to Hot Spring Island doesn't really count) My players and I finished that campaign recently so I am free to put my encounter tables up without fear of spoiling my players. These encounters were meant to provide a challenge for a high-level 5E party but the Umber Hills holds this level of danger most of the time.

Area Summary

The Umber Hills represent a section of the Underdark with glowing hills. It divides a dwarven kingdom (Argentus) from a tiefling enclave (Formosa) and is isolated from the rest of the caverns by underground rivers. Visibility is understandably much better here but the glowing hills seem to shift and change the creatures living within. The only humanoids making their home in the area are a group of deep gnome monks (The Pinnacle Order) who pledge themselves to the dead goddess of balance. 

Source

Umber Hills Event Table

A) EVENT

roll 1d10

1. Bright Lichen, an area where pressure generates light, blinding light. Not moving creates patches of light that burn for 2d6 radiant damage
2. Heart Root, a massive pulsing red root that will flood areas with red sticky nectar that smells of blood (it confers difficult terrain and grabs and sticks at flying things as per the Earthbind spell (DC15 Str Save)
3. Ancient carvings on the hills generate areas of magical darkness, of course, things are hiding inside.
4. Holes shaped like upright humanoids dot the hillside, you get the sinking feeling one of them belongs to you. (Save 15 Wis Save or start looking for yours, if you roll 10 or lower you start to climb inside).
5. A ruined tower looms ahead, a fire burns a bright green inside, you hear whispers (75% chance of summoning a glabrezu)
6. A pall cold fills the hills, treat as extreme cold from the dmg (DC10 con save every hour or gain exhaustion)
7. A buried titan's eye flutters open in waking sleep, it fires beams that slows the movement of whatever moves the most.
8. A large nest is set up amongst the hills, it belongs to something big and there's baby-like mewling coming from it.
9. A sunken temple overgrown with plants comes into view. Singing can be heard from within.
10. The way is clear and the path is peaceful...

B) Creature

roll 1d10

1. Sundew-men, monstrous plants that grow in a humanoid shape. They smell sweet and eat meat. (4d8)
2. 4 cyclops are engaged in a long distance staring contest
3. Something ancient appears, it has 4 heads, 7 wings and seeks to cleanse the hills of sinful life.
4. A troop of tielfing knights (3d4)
5. A group of Pinnacle Order Initiates (2d4) 
6. A chariot pulled by nightmares is chilling on the side of the road, I'm sure it doesn't belong to anyone. (Contains a death knight within that will possess would be thieves)
7.  A creepy gnome salesman is waiting at a crossroads, he sells magical wheels
8. A literature spider (it consumes written language) has made its nest nearby
9. A previous enemy of the party reappears dramatically!!
10. Purple Worm x2 Electric Boogaloo