Which 6* to r3

Doom and Ultron are already r3.
Next two are going to be Ghost and Diablo as soon as I reach lvl 60. I've already formed tech and mystic t5cc too. So, which t5cc should I form next, and for that I'll have to decide which 6* to r3.
My options-



You can check my entire roster here-
https://forums.playcontestofchampions.com/en/discussion/307370/which-content-should-i-do-next-im-thinking-of-lol#latest
I'm also having a science awakening gem.
I'm mainly thinking between cull(sig 100) and corvus(sig 20).
Next two are going to be Ghost and Diablo as soon as I reach lvl 60. I've already formed tech and mystic t5cc too. So, which t5cc should I form next, and for that I'll have to decide which 6* to r3.
My options-



You can check my entire roster here-
https://forums.playcontestofchampions.com/en/discussion/307370/which-content-should-i-do-next-im-thinking-of-lol#latest
I'm also having a science awakening gem.
I'm mainly thinking between cull(sig 100) and corvus(sig 20).
0