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