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