Mayan's Calendar.

{t} Sacrifice Mayan's Calendar:
search your library for the card
"Mayan's sneak attack",
put it in your hand, then shuffle your deck.
The Mayans created an advanced calendar
to help them tell what day it is.
they could use this to figure out when the enemy
(the invading Spanish) where going to attack,
and they could use that info to plan a sneak attack.