Ammo Baron returns in Pirate's Curse and takes over Scuttle Town. He also acts as the first boss in the game, though defeating him is a cinch. He stays in a giant tank and shoots a series of cannonballs, so get on the left platform and jump over the black cannonballs to avoid them. You also want to be on the platform because he occasionally charges forward just short of it.
Periodically Ammo Baron shoots a red cannonball that bounces to the other side of the screen. This is your cue to attack - whip the red cannonball with your hair to redirect it at the tank, which then causes Ammo Baron to fall out of it. Run up there spam the attack button until he gets back in the tank. Repeat the process a few times to finish the fight.
Remember that new pistol you got a little while ago? Well, we're going to make good use of it in this fight. Small eyeballs will appear on the sides of the screen, which you want to attack to raise one of two platforms. You can whip the small eyes in the first part of the fight while you stand on the adjacent platform, but this soon changes. Eventually you'll be shooting the eyes from across the screen while standing on the far away platform, so just get used to using the pistol at all times.
Once the platform raises, shoot directly at the boss to deal damage. It's a very simple process, and the only worry here is the Cyclops Plant's laser attack (which is easily avoidable) and the enemies he spawns in the middle of the screen (which can be destroyed with a few attacks).
The second phase of the fight finds the giant eye bouncing around the screen. Avoid it as best as you can and be extra cautious when it picks up speed. The eye also shoots laser beams in this phase, but you can duck to avoid the blast. If you duck right next to it, you get a bunch of free attacks. Just continue to dodge and hit the boss when it gets close to defeat it.
Empress Spider likes to follow Shantae around and then lunge down to attack her. All you need to do is run around and make sure to dodge the attack; it's all about the timing. Once Empress Spider lunges down, run up to the eye and attack it multiple times. The other way you can hurt the boss is to equip a Pike Ball or Super Pike Ball and then jump up to create contact between the item and the Empress Spider.
Eventually Empress Spider will begin to lay eggs, which quickly hatch into little spiders. Dispatch the extra enemies quickly and be careful that the boss doesn't do the fire attack next. This creates a long line of fire on the ground. The only way to avoid it is to jump and use the hat (press the R button) to glide to the other side. By the time you land, the fire will have disappeared. Empress Spider picks up speed as the fight goes on, but just stick with the strategy and you'll defeat her.
Squid Baron faces an existential crisis in Pirate's Curse and laments his status as a filler boss. And thus begins the fight. The first part shouldn't take too long. Squid Baron will slide across the floor, so jump over him to avoid getting hit. Then he pounds the ground and creates sparks... you know the drill, jump to avoid it. Lastly, he munches on some food to regain health, so run up there and hit him. If you equip Monster Milk you can do more damage per hit than he gains from the food each second.
Eventually Squid Baron becomes Squid Baron 2.0 and encases himself in armor. His attacks are the same but he's a lot faster, so defense becomes even more important. Also, you should notice that all your attacks do zero damage now because of the armor. Well, you need to bounce on his head with the new Scimitar (L Button) to get rid of the armor. At that point he reverts to his old strategies and you can actually hurt him again. Just be sure to defeat him quickly, otherwise he puts the armor back on.
This boss fight is quite a step up from the first few. The end of Dagron's tail is super dangerous, and he swings it around like nobody's business. In addition, he occasionally spits out some kind of acid while swinging the tail, so there are a lot of situations in which you might get hit. There isn't any big secret to dodging, you just have to do your best to avoid his attack. Have some healing items handy just in case.
As for attacking Dagron, you need to use the new burst ability with Risky's Boots to hit the sides of the screen. This will cause platforms to fall down, which you can jump on to give yourself more of a height advantage. When Dagon comes back down, jump up from the platform and hit him in the head. If successful, he will hover at ground level and you can go whack him a few times before he flies away. This is the entire fight, though he picks up speed as it goes on.
Just like the other boss fights, this one requires you to use your new item/ability. In this case, the cannon plays a huge role. Obviously the spots on Steel Maggot's back stand out, and you have to hit them with the cannon to reveal a different weak point. The trick is to do so in the right order. If you happen to hit the wrong one at any time, the pattern resets.
I believe the order in which you must hit the spots on Steel Maggot's back is random, so try a few different combinations until you find the right one. If successful, all the spots will light up green and reveal a red spot on Steel Maggot's tail. Hit that multiple times to deal damage, but be quick about it or the spot disappear and progress resets. When you repeat this process, you must find the new order to hit spots on Steel Maggot's back. Again, experiment to find the right combination and then hit the spot on the tail. Do that a few times and you're done.
The Pirate Master
Pirate Master likes to disappear and then reappear in a new spot, so follow along and hit him when he pops back up. Sometimes he will shoot out a pattern of purple orbs, and the only way to avoid them is to run away to the other end of the screen and jump through the gap that forms. Then some windy platforms appear and Pirate Master seeks protection up there. You can jump up to hit him, but the platforms move all over the place and Pirate Master continues to shoot the purple orbs down at Shantae. Don't get too greedy and wait for the right opportunity to attack.
Pirate Master's one other attack is a series of laser beams, though reticules on the screen show where they will appear. Just avoid those spots, wait for the beams to disappear, and then continue the fight. Eventually a second phase begins... but only if you found all Cacklebats in the game. Otherwise he gets away and the game ends on a somewhat bittersweet note.
Pirate Master takes all your weapons and in turn becomes far more powerful (and a lot bigger). Now he shoots gigantic cannonballs that bounce across the screen and leave little room for error. He also readies a bunch of swords that stab downward, so find the one safe spot in the long line of blades. His last attack involves four pistols that appear in the middle of the screen and spin, shooting out purple orbs that do a lot of damage. Avoid those and get to the next part, in which you can finally attack Pirate Master.
The windy platforms from the first phase of the fight appear again, but now you can jump on them and get to the top. When you're at Pirate Master's head, whip him a few times before he begins the entire cycle again. Keep it up until another little scene plays out, in which Shantae gets her magic back. Now she does a ridiculous amount of damage, so repeat the process a few more times and wail on Pirate Master. In the final part of the fight, you must direct cannonballs at Pirate Master's face with a large reticule. After this he goes down for good and you can enjoy the ending!
Shantae and the Pirate’s Curse Boss Guide
Embarrassing for all involved.
What do these eShop changes mean?
Major league swagout.