Gallery Cards?

[Chaosolous]

One is the final unlock of the battle pass.

What are these even for? Looking at?

[Jet Magnum]

The final one of the Battle Pass appears to be. But as for the others unlocked from the Event missions, most of which involve having to do Team-up tasks and play as specific characters, they unlock small story blurbs that delve into the lore of the time-jumbled maps we're fighting in.