The mines were abandoned decades ago and since that time various groups have moved and claimed the tunnels as theirs. Some come to work the mines, some did not.
Today, various factions control separate parts of the mine and fight to hold on to what they 'own'. Sometimes alliances are made of broken, some slink through the shadows in hopes of rich on the gems hidden in the rock, others simply trying to stay hidden from whatever sent them into this frightful place, others hoping the gems can make them wealthy and powerful.
1- open area/contested, any faction may be encountered here
2- Jango "Dead eye" Darvil and his gang, holed up and storing their stolen plunder in this section, they are currently in a fragile truce with the spiders
3- Xavtheenix the spider queen raises her brood and plans her return to outer planes, the mushrooms have....done things to them
4- Illyana the water spirit and her twin sister Ayllaya spend their time desperately searching for the Arragean Pearl which she believes was lost in the rocks in the bottom of this pool, they will 'insist' any male visitors assist them in their search
5- Mervin Quentin Beauregard Farnsworth III, a rare gnomish druid, hides here from those seeking him for crimes against nature, his magical nature and overflowing magical vermicitude has caused glowing mushrooms to blossom through the mine
6- Bento Happlestep, a brave halfling explorer has been secretly sneaking in and mining to great wealth, he keeps the other factions away by frightening them with illusions from a magical wand, he is terrified of the mutated spiders he has encountered
7- The ogre Bloodfinger Tribe has moved in and began mining, Ovilax Skullsitter sees the gems as a way for him to secure the ogrish throne for himself, he recently snacked on a mushroom which doubled his strength
The mines are quite notorious for their resplendantly abundant gems and crystals. Another well known fact that the rock here is full of the dangerous ore known as rhydonium. Anyone spending the time to mine (with proper equipment) has a 2 in 12 chance (2d6) per turn of discovering a valuable gem or mineral. On a roll that results in doubles however, rhydonium is discovered and immediately and violently discharges, causing d6 damage to all within ten feet of the miner. The miner takes double this damage.
If ore is discovered, consult the table below. First roll for ore discovered, then roll to determine the quality of the deposit. Take the core ore value and multiply by the listed quality modifier. How large this ore is I leave up to the DM.
2-4: Silver, value 1gp
5-6: Electrum, 3gp
7: Gold, 5gp
8: Blue quartz, 10gp
9: Red Garnett, 20gp
10: Rock Crystal, 40gp
11: Diamond, 10gp
12: Viz, 500gp
2-5: Poor, x1
6-8: Fair, x2
9-10: Good, x4
11: Superior, x10
12: Majestic, x50
The mushrooms and their effects I leave to you. Enjoy.