Here is the full list of all 23 Royal Roads achievements.
Help the princess return her former self
Earn all possible trophies in Royal Roads
Beat 100 levels with 3 stars
Tame all kobolds in the Kingdom
Help all griffons return to the kingdom
Beat 80 levels with 3 stars
Defeat all pirates in the kingdom
Sail the archipelago and dock in the Land of the Wizards
Beat 60 levels with 3 stars
Make it to the Azure Shores by tunnel
Stop the disasters in gnome caves at the source
Defeat a kobolt
Open the gates to Gnome Caves
Beat 40 levels with 3 stars
Help all elf villages find ancient altars
Use elf magic
Fix the bridge and move on to the Elf Forest
Beat 20 levels with 3 stars
Help repair all settlements after natural disasters
Use your royal will
Beat 10 levels with 3 stars
Use horses
Beat 5 levels with 3 stars