This answer makes it seem as though it could be a valid choice to randomly decide to have more than 60 cards in a Constructed deck "just in case"
It is also double-checked by our prepress tech against the print specification to make sure it supports all of the printing plate separations necessary for reproduction
Flavor-wise, these diverse spells are contained in the Biblioplex's archives in the campus of Strixhaven, and gameplay-wise, these special cards will appear in regular Strixhaven boosters, with one in each regular booster of the set and more in Collector's Boosters
For example, if your opponent targets your Varis, Silverymoon Ranger with Magic Missile, you can announce the ward trigger and ask if they'd like to pay it
Some cards in Duskmourn: House of Horror have alternate artwork (and collector numbers) from their main set counterparts that contain a monster of Duskmourn lingering in the background
For starters, its seeing play in pretty much all the same decks as Lightning