By the way, since coming across this forum, it's been stuck in the back of my head and every time I see a card referencing another card, I immediately think "I
wonder if anyone's mentioned that yet." I'd love to see if you ever get something semi-functional going with this concept, but mostly it's just fun to notice a unique feature that not very many cards have.
I also laugh a little at the number of people commenting cards that search for a specific card even though you specifically said you were avoiding those, though I will argue against your claim that
Peer through Depths, et al. just search for a card, since, yes, they find
The Unspeakable, but to work, you have to first cast all three spells on the same turn. If you changed the text from "search for
The unspeakable and put it into play" to any other effect (like, destroy target creature or gain 10 life or even a less specific search), you'd definitely include the three spells as part of the deck.