Case of the Shifting Visage (Murders at Karlov Manor Commander)

Enchantment Ñ Case - At the beginning of your upkeep, surveil 1.
To solve Ñ There are fifteen or more cards in your graveyard. (If unsolved, solve at the beginning of your end step.)
Solved Ñ Whenever you cast a nonlegendary creature spell, copy that spell. (The copy becomes a token.)