I'd just like to say that I've come across a pretty solid method for beating Neptune. You have to get Electrocutor out semi-early to lobo his Squids, but other than that, it goes like this:
1) Fractal RoLs twice, hard and fast, getting as many as you can so you can build lots of
before he puts out Flood. Always keep a spare RoL in your hand just in case he manages to kill them all before you can Fractal again (never happened to me, but it could.)
2) Get Hope out ASAP, of course.
3) Even if Flood is out, put down the first Light Dragon you can Fractal, and Fractal it. Keep the remaining Dragons in your hand.
4) (Assuming Flooding has come down by now) let him kill an RoL, and fill the space with a Dragon. He'll leave the RoLs along for a few turns while he kills the Dragon.
5) Use those turns to build up
quanta reserves, and keep replacing the Dragon whenever it dies. Neptune will slowly lose HP over these turns assuming your Dragon doesn't get frozen by the Permafrost. Even if he does, it's OK.
6) If Neptune kills RoLs while your Dragon is frozen, you might need to Fractal them again to keep plenty of backup in your hand. You don't want your Hope (or
production) to drop below 6 per turn.
7) He'll eventually put down an Arctic Dragon or two. Just suck it up. SoGs will eventually negate most or all of the damage.
8) Eventually, you'll blow through your reserve Dragons, but you'll also have 100+
quanta in reserve. Fractal your last Dragon, and play them all regardless of the Flooding. You should almost always do enough damage to finish Neptune off.
It's actually not hard at all once you get the hang of it.