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