Knights and Bikes

As of 9-2020: if you are playing on-line and not the host (playing Nessa), you won't get this achievement. You can run through Day 5 after the game is complete (running solo or flipping hosts) and you should be able to get all 6 creatures. The 6 you are looking for are:

Flaming Sword (fire sword thing)
Big Genie (guy that puts poison around him)
Silver Gauntlet (the hands)
Letter Ball (ball with a bunch of letters)
Furry Golf Ball (self explanatory)
(Flaming) Piskie Head (ball that shoots fireballs)