Thanks for the feedback! "Letter Swap" is the amount of letters you can swap each turn. Once you get all the letters, the numbers on the dice become extra exchanges. I hope my explanation has made everything clearer for you now. Unfortunately the second level spirit power has a bug that can make it difficult to defeat the spirit :(. Thanks for playing until the end!
If you click on a letter already added to the board that is not in the correct position (letters in the correct position are indicated by green) you can swap it with another letter that is incorrect, by clicking on this other letter. The yellow letters indicate that the word contains the letter, but that it is in the wrong position within its respective word. This way, you can swap the letters on the board to find the words that represent clues about the spirit you are facing.