You can acquire this knowledge by completing the optionnal puzzle that require you to jump accros 3 light circle (Puzzle N°6 on this link https://grumpygreen.cricket/sycrakea-puzzles/)
When you'll acquire this knowledge you may get a low grade, dont worry! just delete this monster knowledge do the puzzle once again and you'll get another grade. Do it until you get S (take me and a friend less than 4 tries).

TIPS: If you dont want to climb all the cliff in order to restart the puzzle, juste click "select character" you'll get out of the dungeon instead of going onto the char selection page, which allow you to re-enter fast!