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