It's certainly not appropriate nor legal to bury a junction box inside a wall. That should never have been done.
I agree with JACK that this looks like pretty normal chain wiring: one of the larger wires comes from supply and the other one goes onward to other lamps. The smaller wires were pigtails to a former lamp which is now gone.
I don't know what the story is with the two splices in the foreground. I assume those were once possibly soldered? But otherwise, competently executed friction-tape splices. If they still look in good condition, you could continue them in service. Otherwise you may need to remove all the friction tape and vinyl whatever-that-is, and put wire nuts there. If it's soldered you are probably better off just re-wrapping it.
If you want to put a lamp there, you can add the lamp's wires to the bundles if you wire-nutted it, otherwise pigtail the lamp's wires to the existing pigtails.
Otherwise put the wires back into the junction box and cover it with a blank cover plate.