The two files monster_umor.txt and monster_comb.txt are Angband 3.0.5 edit files.
The former contains approximations to the old UMoria 5.x monster list, while the
latter contains copies of the monsters which were found in that version, but not
in Angband, such as Clear Yeeks or the Evil Iggy.
Note that some monsters had a "corrosion" attack in Moria, instead of an acid attack.
These monsters are only found in the _umor file, and have been converted to the acid
attacks. Also, defeating the Balrog does not seem to terminate the game as it should.
There are 680 monsters in monster_comb, and 280 in monster_umor.