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