#both derive their powers from childhood tragedies that left them orphaned

[div-divington]

Not to be cringe but...

Tall-ass tower manifests in city without any logical explanation

Interior has nonsensical geometry and architecture. Building shifts constantly. Seemingly alive.

Shady organisations have tried to manipulate the structure to their own ends.

Linked to an extra-dimensional godlike entity that wants to use the tower to bring about their own goals (Nix and The Board respectively)

Protagonists unlock their powers by pointing a "gun" that isn't actually a gun at their own heads and pulling the trigger (the Service Weapon is obviously very different to an Evoker but the symbolism is there I think)

Both do this without being certain they'll survive.

Protagonists have manifestations of their inner selves and their willpower living in their heads. These manifestations are sentient beings that serve as both an extension of the protagonist and a separate character.

Both of their inner selves also serve as extensions of a separate entity (Thanatos (the Persona) is a remnant/extension or something of Ryoji. Polaris is an offshoot/remnant of Hedron)

Protagonists are guided and assisted by otherworldly beings who take the forms of older men in service roles (Ahti, who presents himself as the janitor of the Oldest House, and Igor, who acts as the host of the Velvet Room)

Ahti and Igor both appear to exist in a way distinct from humans and can perceive other planes of existence easily.

Ahti and Igor both speak in manners that the protagonists find confusing and aloof but ultimately are trustworthy and good-natured beings.

I've run out of picture slots, tragically, but do you see the vision?

I think a very fun crossover fic or something could very easily be made here.

Additional things for the Oldest House and Tartarus:

Filled with monsters that feed on human consciousness and leave people as husks of their true selves (Shadows and the Hiss)

Filled with fun little lore documents left behind by researchers.

Directly connected to planes that exist between dream and reality (the Velvet Room and the Astral Plane)

Heavily based on mythology (Tartarus is obviously named after, y'know, Tartarus. The Oldest House is heavily implied to either be Yggdrasil or at the very least be an ancient tree that potentially somehow inspired the myth of Yggdrasil/took its form from said myth).

You Are Going To Get Lost In These Funky-Ass Towers.