Here is the full list of all 36 ValeGuard achievements.
Unlock the Engineer Class
Construct a trebuchet
Complete a campaign without losing any heroes
Give troops a mount
Unlock the Hexblade Class
Train a Monk unit
Build 10 Frost Towers
Fight off a mushroom invasion
Gain a level from 'Training in a Bottle' potion
Give a hero a mount
Unlock the Barbarian Class
Suffer defeat
Acquire 5 enchanted wells
A hero dies in combat
Defend a town without building a tower
A hero reaches max level
Unlock the Alchemist Class
Train a Longbow Unit
Train a Berserker unit
Repel an undead attack from the graveyard
Fight off a bandit attack
A troop unit reaches max level
Destroy a Goblin War Rig
Complete the ValeGuard Tutorial
Open the Help Menu
Complete a campaign on ValeGuard difficulty
Acquire a Harvest Guardian
Defend a town without making troops
Train a Templar unit
Acquire the Golden Lute
Become the Skeleton King
Get the firework effect from a mystery potion
Unlock the Druid Class
Unlock the Wizard Class
Unlock the Summoner Class
Unlock the Rogue Class