The descriptions each uniquely clue a monster from the rogue-like game 'Angband', which is also called the 'Mines of Moria' or the 'Hells of Iron' by Tolkien. The exact names of the monsters may vary based on the version of Angband used, but both version 2.7 and 3.0 should work. The monsters are:
Feagwath the Undead Sorceror
Blubbering icky thing
Spirit naga
Killer blue beetle
The Queen Ant
Drolem
Bloodshot eye
Black naga
Azog, King of the Uruk-Hai
Squint eyed rogue
Hummerhorn
Bolg, Son of Azog
Medusa, the Gorgon
Clear icky thing
Carcharoth, the Jaws of Thirst
Ugluk, the Uruk
The Tarrasque
Gorgimera
Boldor, King of the Yeeks
Death drake
Giant grey rat
Orc shaman
Green glutton ghost
Radiation eye
Guardian naga
In Angband, like any text-based roguelike game, the monsters are all represented as letters. The letters of the clued monsters, taken in order, spell 'LinKage not IoniC oR HyDroGen', which is COVALENT BOND.
2006 MIT Mystery Hunt