Lydia Frye can't be blocked by creatures with power 3 or greater.

At the beginning of your end step, surveil X, where X is the number of tapped Assassins you control. (Look at the top X cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)

""I would settle for the right to vote." —Lydia, to Winston Churchill"

Rulings

Once Lydia Frye has been blocked, increasing the blocking creature’s power to 3 or greater won’t cause Lydia Frye to become unblocked.2024-07-05
The value of X is calculated only once, as Lydia Frye’s last ability resolves.2024-07-05