Here is the full list of all 55 SpellForce 2 - there are Demons of the Past achievements.
Complete Westguard
Kubi rule them all
The developers law
Complete Stepping Stones
Complete Realm of the Gods
Complete The Citadel
Complete Depths of Kul’rath
Complete Remains of Steelcoast
Complete Shadow Realm
Complete Icewastes of Shalibar
Complete Forest of Argan
Complete Demons of the Past on Easy or Normal level
Complete Demons of the Past on Difficult level
Complete Demons of the Past on Very Difficult level
Collect Armory of the Eo
Cast 40 Fireballs with the avatar
Charm 50 enemies with the avatar
Conjure 66 demons with the avatar
Get invulnerable 75 times with the avatar
Get 20.000 gold from rewards
Get 50.000 gold from rewards
Cast Battle Cry 50 times with the avatar
Hit enemies with Slash 50 times
Cast Salvo (Master) 40 times
Cast 200 shaikan spells
Reach level 10 with the Avatar
Reach level 20 with the Avatar
Reach level 30 with the Avatar
Complete the Twiddle quest chain
Kill the Lich without him spawning back once on Difficult or Very Difficult level
Save all the villagers and farmers on the map
Catch Darc before he can run around even once
Sneak throu the city of Zerbo second times with the Mace of the Guardian on Very Difficult level
Kill all city guards in the city of Zerbo after the main quest (Mace of the Guardian is needed!)
All of the dwarves must survive in dungeon of Niethalf on Difficult or Very Difficult level
Destroy the ballistas, the evil spirits and the portal without any help.
Kill every monster in the arena.
Yes you do!
Close every gate after opening them
Change your mind three times
Complete the 'The Citadel' map on Very Difficult level
Find the lost orc soldiers
Kill all the huge spiders on the mounds
Win the duel against the Shaikan boss at the first attempt
Hunt all the escaped monsters
Kick the seal with all the fire golems
Break all the mind walls of Sariel in 10 minutes on Difficult or Very Difficult level.
Kill the beast with the seal without trapping it on the bridge.
Destroy the Demon base only with Shadows
Walk through the maze without harming yourself
Get the "parrot" alive
Get the puzzle key without killing the Lich on Difficult or Very Difficult level
Destroy the southeastern Nameless base within 20 minutes on Difficult or Very Difficult level
Collect every power crystal and power every tower before attacking Zazhut
Find the mysterious green relic