Speaking of puzzles…here’s the concept for a literal puzzle-board that we talked about. The bottom of the board is an open puzzle and you complete the puzzle as you complete spells, adding a piece each time a spell is cast.
In this concept, it could work in different ways:
(1) the puzzle pieces depict a tableau of the solstice party itself (so you would draw a puzzle piece and add it after completing a spell, still represented by a card), similar to what Ben described
(2) the spell “cards” are actually in the shape of puzzle pieces, and players lock them onto the board after completing them.
a. The art could be “zoomed in” on that specific item, so it would look like a row of magical things (maybe on a shelf or?) or
b. The art could be “zoomed out” to show the party tableau with that item somewhere on the puzzle piece in a more detailed/complex party scene.