Gargoyle Pebble

{t}, Return another artifact creature you control
to its owner's hand: Mature Gargoyle Pebble. Activate this ability only any time you could
cast a sorcery unless another artifact creature
you control is the target of a spell or ability an opponent controls. (To mature Gargoyle Pebble, exile it. If you do, search your library for a
non-Young creature card that shares a creature
type with it. You may cast it by paying the
difference in mana costs between it and this creature. Then shuffle your library.)