How 'bout the Forest's Eye is a gem that sucks in sunlight from far away and shines like the sun. The caves leading to it would be really dark (light being leeched to the Forest's Eye). At the eye, there is an underground forest where the light from the Eye bursts forth and is reflected off a cavern ceiling of reflective crystals. Then hit them with evil fey, or something. I published one that you could use (The Goblin Fair, Airweaver Games) - it's OGC - called the Arachnafee.
Arachnafee
Medium Size Fey
Hit Dice: 4d8 (16 hp)
Initiative: +4 (+4 Improved Initiative, +3 Dex)
Speed: 30 ft.
AC: 17 (+4 natural, +3 Dex)
Attacks: longsword +3 (+2 Str, +1 weapon focus, +1 base) or longbow +4 (+1 base, +3 Dex)
Damage: longsword 1d8+2 or longbow 1d8
Face/Reach: 5ft by 5ft / 5ft.
Special Attacks: spell-like abilities
Special Qualities: immune to spells of enchantment school, darkvision 60 ft., freedom of movement.
Saves: Fort +2 Ref +5 Will +5
Abilities: Str 15 Dex 16 Con 11 Int 11 Wis 16 Cha 15
Skills: Hide +4, Move Silently +4, Listen +4, Spot +10, Climb +10, Jump +10
Feats: Improved Initiative, Weapon Focus (long sword)
Climate/Terrain: Any Forest, Underground, Haunted/Magical
Organization: Solitary, Pair, or gang (2-5)
Challenge Rating: 4
Treasure: standard
Alignment: Usually CE or NE
Advancement: by character class
The arachnafee are evil fey creatures, friends of spiders and the darkness. They are capable of speaking with and commanding ettercaps as well as monstrous spiders. Their original homes are in fey realms shrouded with spells and spider webs, and they are the source of several stories told to frighten children into good behavior. It is said that they steal babies and change them into ettercaps. Arachnafee look like elves with wrinkled grey skin and bulging black eyes, and they have the elven immunity to charm spells. However, if they are related to elves, the split happened so long ago that it has been forgotten.
Combat: Arachnafee can cast a web (spell-like ability) twice per day. They can move freely in their webs, and so can spiders and ettercaps. They will cast web spells and then fight in them, using their freedom of movement (and that of spider allies) to gain an advantage. Most arachnafee with class abilities are sorcerers or druids.