There are multiple "Mob Lists" available... I'd say the main one would be called "PS_GameDefs" (get it?)
Using simple queries on that database, would get you the information you need. I.E.
Code:
SELECT * FROM PS_GameDefs.dbo.Mobs WHERE MobName LIKE '%Cryptic The Immortal%'
The above would get you all the listings of 'Cryptic The Immortal' which has mob IDs, and all the information you'd need.
If that doesn't work for you, you could do:
Code:
SELECT * FROM PS_GameDefs.dbo.Mobs
Execute it, then right-click the results and save as .csv
There you go, your own Excel mob ID list