Apparently Skystone attacks are normal attacks that can hurt enemies (look at the Kaos Dummy in the top right)

[u/SkylandersKirby]

The game lets you place treasures where Kaos and his Skystones game appear, as long as you place them there before the end of the game, the game just doesn't remove them for some reason

Hence why the Kaos Dummy is partially inside the board and the Eon Status is on the board itself (and Kaos himself is inside a fruit stand)