Case of the Filched Falcon
Enchantment - Case
(CMC 1)
When this Case enters the battlefield, investigate. (Create a Clue token. It's an artifact with ", Sacrifice this artifact: Draw a card.")
To solve -- You control three or more artifacts. (If unsolved, solve at the beginning of your end step.)
Solved -- , Sacrifice this Case: Put four +1/+1 counters on target noncreature artifact. It becomes a 0/0 Bird creature with flying in addition to its other types.