Here is the full list of all 20 King Lucas achievements.
Organize 20 searchs in multiplayer mode.
Complete one search before anyone in multiplayer mode.
Participate in one search in multiplayer mode.
Use invencibility potion 20 times.
Walk 750 rooms.
Use life potion 10 times.
Reach the rooftop terrace of the castle.
Use 50 keys to open doors.
Find the frog Princess.
Unlock all rooms in one castle.
Use the compass in one search.
Kill 200 enemies using ice sword.
Finish with 200 enemies using fire sword.
Walk 250 rooms.
Finish with 150 enemies using magic stick.
Complete the search of 3 princesses.
Finish with 50 spiders.
Complete the seacrh of the dog William.
Finish with 100 slimes.
Walk 100 rooms.