I've combed through Underdark. Please note that contrary to my earlier decision, alchemist's mineral acid will be allowed, though at a very slight cost increase. What follows is a list of acceptable equipment, magic items, domains, and spells from Underdark:
Martial Weapons:
Razored armor--similar to armor spikes
Razored shield, light
Razored shield, heavy
Exotic Weapons:
Nekode--glove or strap fitted with spikes in palm. Useful for armed attacks and climbing.
Steel fins--kuo-toa glovelike weapon with sharp steel claws
Flutter blade--deals piercing or slashing dmg
Pincer staff--will provoke an attack of opportunity but only from adjacent foes
Armor:
Nightscale--similar to leather armor but reduced armor check penalty and spellcasting failure
Chitine web--armor woven by chitine that degrades over time but is light category
Spidersilk--light and soft to wear, attractive to those with low strength scores
Tentacled hide--bonus to trip attacks
Stonemail
Feeler plate--reduces miss chance due to concealment
Heavy plate--forged for the strongest of warriors. Weight 100 lbs.
Non-magical Armor qualities:
Buoyancy--increases odds of being able to swim if underwater
Camouflage--cost adjusted to +500 gp--bonus to hide
Muffling--cost adjusted to +500 gp--bonus to move silently
Stability weights--bonus to balance and checks made to avoid being bullrushed or tripped
Other Non-magical Equipment:
Alchemist's mineral acid--cost adjusted to 30 gp--splash wpn, deals dmg to earth subtype creatures or dissolves inert rock/stone
Blackwater--taints water
Caveharp--instrument grants perform bonus and sound carries in tunnels
Darkoil--protects drowcraft weapons and armor from effects of sunlight
Darkvision-invisible paint--leave messages invisible to creatures w/darkvision
Shriek paste--reacts to torch light
Spelunker's kit--cost adjusted to 100 gp--aids with several spelunking skills in cavernous areas
Poison:
Cave terror--ingested, tough to resist, somewhat expensive
Drow knockout poison--injury, easy to resist, fairly cheap
Sickstone unguent--injury, tough to resist, expensive
Stun gas--inhaled, easy to resist, cheap
Magic Weapons:
Bloodthirsty--adjusted to must kill 4HD creature minimum every 12 hours--+1 wpn that can function as +2
Drowcraft--energized by faerzress, grants bonuses
Sizing--can alter wpn size
Finder--bonuses to underground skill checks
Blindsighted
Magic Armor:
Drowcraft--energized by faerzress, grants bonuses
Halfweight--expensive but halves armor weight
Illithidwrought--must rp purchase/availability with DM--provides insight bonus to AC
Xorn movement--move through earth as xorn.
Rings:
Antivenom, frugal
Antivenom
Detect thoughts
Enslavement rings--expensive
Rods:
Dowsing rod--find potable water
Portal finder
Faerzress negation
Dead--increases caster level of wielder to deal with undead
Webspinning--spiderskin effect, access to web, freedom of movement
Staffs:
Spider
Shadow, lesser
Shadow, greater
Underdark
Stone
Watery grave
Portals
Wondrous Items:
Daylight pellet
Web choker--somewhat similar to necklace of fireballs
Rope of climbing, greater
Sun flash pellet
Figurine of illusory escort--useful for intimidating others or creating impressive but illusory cohort
Lurker cloak--polymorph into lurker
Messenger medallion--send message
Lenses of clarity--reduces miss chance due to glamer spells
Gloves of burrowing--can burrow up to xxx amounts of minutes/day
Spider mask--darkvision, fort bonus vs saves to some poisons, immune to web
Figurine of wondrous power: jasper spider, sardonyx stone flyer
Mantle of energy resistance--can be bought for one or more types of energy
Cloak of stone--bonuses to hide, move silently, access to meld into stone
Antimagic torc--create temporary antimagic field
Gauntlet of disintegration
Glove of venom--very nasty poison spell xxx times/day
Boots of tremorsense
Driftdisc--extremely expensive, traveling disc oft used by powerful drowess matrons
New Domains:
Balance
Portal
Watery Death
New Spells:
list will be forthcoming, hang tight