Ancestral Knowledge
{1}{U}
Enchantment
Cumulative upkeep {1} (At the beginning of your upkeep, put an age counter on ~this~, then sacrifice it unless you pay its upkeep cost for each age counter on it.)
When ~this~ enters, look at the top ten cards of your library, then exile any number of them and put the rest back on top of your library in any order.
When ~this~ leaves the battlefield, shuffle your library.