Viviane, Lady of the Lake

This spell cost {1} less for each artifacts
you control.
When Viviane, Lady of the Lake enters the
battlefield, mill the top four cards of your library.
{t}: Choose target artifact card in your graveyard.
You may cast that card this turn.
In the midst of the lake Arthur was ware of
an arm cloathed in white samite, that held a
fair sword in that hand.