Cartesian Librarian

Dense
{3}{u}{t}: Exile the top card of your library and
place a book counter on it.
When a Cartesian you control is killed by a rogue,
a poacher, or a pirate, put those cards into
your hand. Otherwise, you may pay {u}{u} to put
one of those cards into your hand. Sacrifice
Cartesian Librarian.
Beautiful things need to be preserved.