Do you have Top Droidragon?
You actually do have a team!
DJ lead / CDD / Black Baron / RK / echidna (if you want delay for emergencies) or (toytops for second heart maker option) / Max awoken GrOdin friend leader.
For Neptune you will activate black barons Guard Break, it should be enough for Hell Ball and Gungnir to do enough damage, it will probably take a few activations to kill him but its doable.
Its not guaranteed you are going to 0 stone it the first floor will be the hardest especially if you get synced mobs. It sucks you don't have Siren for auto heal but just hope your Odin friend auto heal will be enough. Basically your going to have to make 3 combos plus heal almost every turn.
here
http://puzzleanddragonsforum.com/showthread.php?tid=8266