'Fateseal' was introduced during the Timespiral block on two Future Sight cards. Mesmeric Sliver and Spin into Myth

702.17. Fateseal

• 701.17a. To "fateseal N" means to look at the top N cards of an opponent's library, put any number of them on the bottom of that library in any order, and put the rest on top of that library in any order.

Translation:

• 702.17a Look at the top N cards of an opponent's library. You may choose to put them on top or on the bottom of that library in any order.