You know, since the Apostles were brought back up. It's kind of reached the point where we can say for sure what the 5th and 8th Apostles are. Since that's the case. Let's throw some names around for them since it's highly possible that they're Time and Light.
For the 5th, if it's Time, I would call it Eternity to go with Ether(The 6th). I can't really think of anything else. Well, maybe Mobius, short for Mobius Time Loop. Think it has something to do with Mobius Strip but it goes above my head at that point.
For the 8th, if it's Light. We can go with Radiant, Radiance, Brilliance, or Dawn. Since the 7th is called Lord of Dark or Dark King, these would be fitting as an opposite to them. Especially Dawn since it means "First Light". Lord of Dawn. I still hope it's a busty Light Mommy. Well, it's likely dead now but you never know what corpse we'll stumble upon out there. I ain't saying I'm going to defile my hypothetical Auntie 8th but.....
Anyway, that's all I came up with. I probably could've thought of more for the 8th but the 5th is difficult, at least for me. We'll have to wait for the reveal of 9th through 12th before even getting to their names.