Cave Story walkthrough for the Hell speedrun. -by Derakon

My best time so far is 4:53:0, netting me the Toroko-themed menu screen.
I'll just walk through my overall process.

First, get the Booster 2.0 and rescue Curly. Rather obvious, that. Be
sure to pick up the Nikumaru Counter as well, since this is, after
all, a speed run. I also strongly recommend using the Spur, since it
utterly obliterates Ballos' first 2.5 forms.

Next, clear the "normal" ending bosses. Try to conserve missiles; they
don't get replenished between the death of the Undead Core and the
escape sequence. Also, and of course, make it to the Prefab Building
without losing any health. Far better to redo those four bosses than
to start your Hell run with less than perfect health.

Before jumping into the hole, equip the missile launcher. You're going
to power it up to level 2 in the first room. That means hitting the
first two experience boxes at the very least. Try to hit the other
four as you fall down the pit. Shooting them just before Quote
completely overlaps their sprites should get you the right timing. You
should be almost all of the way to level 3 now. Nab the health and
pick up Curly.

This next room is rather chaotic. Sometimes I make it through without
taking any damage; most times I'm out 20-30 points. Use level-2 Spur
shots to take out angels whenever they get in your way, but do
remember that getting hit by an angel only costs you 5 damage, while
the falling stones cost 10. Make excessive use of the Booster 2.0
here; this room was designed to get you to do some fancy flying. If
you aren't boosting forwards, you should be either on your way to the
ground to recharge the booster, boosting up to dodge something, or
boosting backwards to dodge something else. Don't walk; it wastes
time.

The third room mainly is a measure of how good you are at handling a
continuing offensive. You shouldn't stop to kill enemies unless you're
waiting on a door to clear. So for example, the first door is guarded
by two Butes and two Mesas. Use a level-2 Spur shot to hit the door
over the Butes' heads, then kill everything you can in the time you
have before the door clears. Boost through it, charge up a level 2
Spur, and hit the next door. Make good use of Curly's ranged Nemesis
to clear the blocks hiding health (in the upper-right corner right
next to the door) while you take out angels with uncharged Spur shots.
Race through the door as soon as it opens, and take out the next door.
Not much to do here while it clears, so just catch your breath.

As a side note, you'll notice that I don't use the Nemesis much.
That's because it's all too easy to accidentally pick up some
experience, and bam - there goes half of your offensive capabilities
with that weapon. And no, I don't particularly feel like getting hit
to level it back down.

The next two "rooms" of this section are rather hellish (right...),
being filled with lots of archers. It's usually somewhere in this
section that I use the Life Pot. My best advice is to get through
quickly, and don't worry too much about killing everything. Remember
that you can always kill flying angels while you wait for doors to
clear. Otherwise, don't bother.

Grab the missile expansion in the last room before Heavy Press, and
for goodness' sake, don't land on the spikes. I usually take out the
lowest of the three doors, just because it makes keeping a handle on
the flying angels easier. So clear the door, fly through, grab the
missiles, and head down to that lower island next to the double doors
leading to Heavy Press. While a door is counting down, continually hop
up and fire the uncharged Spur to keep the angels under control. When
the second door clears, charge up a level 3 Spur shot and head in to
meet the big guy.

Unload that level 3 shot on Press, dodge his attack, and switch to the
Nemesis. If you stand right underneath him and fire upwards, then both
your and Curly's shots will hit him. Rapid mashing of the fire button
will ensure that he dies before firing another shot. Don't get
crushed, but also don't stick around for powerups. There's no time. At
this point, I still had about 20-30 health left for Ballos' three
forms; plenty if you know what you're doing.

Fall through, take the door, listen to the dog's plea, and enter the
seal chamber. Start charging the Spur as soon as you land, and boost
over to Ballos. He's vulnerable the instant he raises his hand;
continue charging until them. He'll charge at you along the ground,
then up into the air, horizontally in air to you, and then back to the
ground. Upon landing, he'll unsettle the bones on the floor. You want
to hit him on his horizontal dashes. You only have time to charge a
level 2 Spur shot, but that's fine. Do be careful, as the amount of
time he spends on the ground between dashes is random. You can tell
when he's about to dash because he'll change his stance slightly. When
he flies into the air, switch to Nemesis and make like he's Heavy
Press. Same concept, same result - he'll go down before loosing a
single lightning bolt on you.

Now, switch to the Spur and shoot down a bunch of the Green Demons
flapping about in the air. They'll drop experience; use it to fully
power up the missile launcher. Then switch back to the Spur. Don't get
landed on.

Ballos's second form will hop into the air, attempting to crush you.
Every time he lands, he'll scatter bones. On his first run, he'll hop
twice before pausing; after that, it's three hops before the pause.
Wait for the pause, then jump up, unleash a level 3 Spur shot, quickly
charge to level 2, fire that off, and repeat once more with the last
of your Booster juice. Done properly, a Spur shot will continue
through both eyes, racking up massive damage (150 points for a level 3
shot, 75 for level 2). Improperly-done, the shot will just impact on
his armor, doing negligible damage. This, therefore, is a chance to
practice your marksmanship.

When Ballos runs out of health, he'll spawn those satellite eyes. Take
as many out with a charged Spur as you can, then switch to Nemesis. If
you find that you don't have any good targets at the moment, feel free
to charge up some Spur shots for when things open up a bit. I haven't
really optimized this form. Of course, don't get hit; you can walk
between the satellites while they're on the ground, and the skulls
they drop in air are dead-easy to dodge.

Having taken out all of Ballos' satellites, he'll spawn those
platforms. Hop up on the left side, and stay slightly above center.
When his armor finally cracks open, drop the level 3 Spur on him, then
switch to the rocket launcher and jump on him. Yes, that's right.
There's actually a safe point you can stand on right next to his left
eye. Not that it matters much; hammer the fire button and your level 3
missiles will toast him in under a second. And that's it! The timer
stops as soon as you land the killing blow.

Good luck!