Here is the full list of all 24 Royal Offense achievements.
Level up any hero during mission to level 3.
Get the first kill.
Kill 50 rats.
Hire 100 mages.
Hire 100 archers.
Build 3 buildings.
Build biggest castle in kingdom.
Level up any hero during mission to level 5.
Level up any hero to level 9.
Get 30 kills with just one unit or hero.
During single battle hire 300 heroes.
Hire two holy heroes at same time.
Hire 666 dark heroes.
Kill 3 enraged enemies.
Headhunt for 10000 silver.
Earn 10000 gold.
Repair any building.
Kill a Troll, save the Lady.
Upgrade any weapons or armor to max level.
Win any silver or gold level without any troops.
Kill weaken enemy.
Get 10 Silver Medals on same mish.
Get 5 gold Medals on same mish.
Get a diabolic number of Medals. ^T^