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