Here is the full list of all 15 Willy-Nilly Knight achievements.
Go through the whole game and find out the final of the story
Finish one of the love story lines
Find the unique Excalibur sword
Visit all the locations on the World Map
To present Idril with something very important
Find out who is Arthur's true enemy and the root of all evil
Gather the team of all 4 characters
Help the little girl to go back home
Destroy all the bosses in the Castoff Dungeon
Kill the wolf leader
Fall in love with Guinevere
Fuel up Bob's still
Kill the boss in a Spiders Crypt
Complete first Siegfried's task