Covetous Niffler

When Covetous Niffler enters the battlefield, its controller gains control of all artifacts in play.
That player can use and controls all artifacts
that it gains control of this turn.
Covetous Niffler must block all artifact creatures,
but will gain control of them when he does if.
he is not destroyed.
When Covetous Niffler blocks any non-artifact
creature, return all controlled artifacts back to
their controllers.