If Hextech Ray's target becomes illegal after it's been placed on the chain (due to Retreat returning it to hand), can Hextech Ray change to target a different valid creature?

Ruling: No, Hextech Ray cannot change targets. Once an item has been finalized to the chain with its target chosen, there is no rule that allows you to go back and change targets even if the original target becomes illegal.

Sequence:

• Step one: When playing Hextech Ray, you make necessary choices (including target selection) while the item is still pending
• Step two: Once those choices are made and the item is finalized to the chain, the targeting is locked in
• Step three: If the target later becomes illegal (such as being returned to hand), the item cannot retarget