Would it be legal to have a note of some sorts that says: Pay for the Pact. So that you would be able to put it on top of the deck to remind yourself to ... wait for it... pay for the pact that you casted last turn?
Yes, as long as you make the note within the current match. You can’t use a note from outside the current match. The note also can’t fully obscure the top card of your library. (Use a dice or bead or something. It’s easier.)













