They exist in the command zone, and are used in a face-down deck of at least 20 cards, or 10 cards for the Duskmourn variant
Duskmourn: House of Horror Prerelease events begin September 20, 2024, at your local game store
The Big Two Daretti, Scrap Savant Daretti, Scrap Savant is the one planeswalker that may be the exception to the not-tournament-playable rule for two reasons
The fight is totally secondary, but combining the two effects can be a massive life swing and board swing if you have 6 mana to spare
The divider above the cards flavour text has a little fountain pen icon at its leftmost point, denoting that this text was written by Lorcanas designers, otherwise we would have seen a little book symbol for direct quotes taken from the movie
(2024-02-02) The face-down spell has no mana cost and a mana value of 0