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