{T}: Mill two cards. (Put the top two cards of your library into your graveyard.)
{2}, Exile this artifact: Shuffle any number of target cards from your graveyard into your library.
Mana cost
2
Mana value
2
Printings
From
$0.32
EDHREC rank
#2029
Buy
Formats
Pioneer
Legal
Modern
Legal
Legacy
Legal
Vintage
Legal
Commander
Legal
Rulings
20 Sept 2016
You can activate Perpetual Timepiece's second ability with no targets just to shuffle your library. If you choose any targets and they all become illegal targets, the ability won't resolve and you won't shuffle your library.