Hollow Island

This boss is a summoner, as she gets damages, swarms of bats come to attack and I mean SWARMS. The closer to death she is the more and more bats you will face.
It is advised to have AOE attacks or at least melee that strikes multiple enemies, because of the spikes on the floor its hard to run around shooting at it.

The strategy that worked for me is to face her as a tank, using food to boost my HP regen/dmg and having 150% armor, took me a while but I took her down and never went down below 50% HP.

I got the titanium set after the battle, and oh boy! it would have helped!
Along with a high damaging weapon that hits multiple enemies and removing her armor with Gilded Bolts, I just chased her down, doing some damage and healing myself, took me a minute.

Here is a video of how I did with using the Titanium set then the steam rifle and after that a clip of how I suffered without them.]

This boss lives in the ruins of Sector A1, to get to him you will need several keys to get to his lair, read the F.A.Q. for more details.

Once you get to him, the fight is going to be long unless you have the right tactics to defeat him.
First, you need to remove his colossal armor, gilded arrows do the trick, Klein sells them.
Second, you need to kill at least 1 of the repair robots, these robots heal his HP AND his armor, I dont know by how much but my estimate is around 15 to 20% each, so letting both repair robots reach him will get him back to full very quickly.

For that reason, do a test run and see if you can kill at least one of the repair bots before they reach the lord, if you can do it consistently, you are going to be able to defeat him.

He has 3 attacks.

He throws a boatload of fire missiles at you, these are deadly if you stand in the fire too long as fire stacks get applied to you, you will burn for an insane amount of damage each second.
He shoots steam clouds at you, they are slow and packed close together and easy easily dodgeable.
He shoots cannonballs at you, same as above but even easier to dodge.
Here is a video of how I did it with almost full Feral Armor with Titanium Greaves.

In the southern desert (SW island), there is a tomb in the middle.
You need to use the primordial pickaxe to very slowly open it.
Here is a video if you want to check it out.

These are not bosses but super tough and they are like landsharks.
They live in the SW island, you will need a Springboard to jump the bridge at A3 and get there.
You cannot tank these things, shoot and run!
If you stand on a paved tile, they wont attack you, use this to step into the sand, quickly back away into pavement and shoot at them while they jump but beware the scorpions, you can cheese them using clever use of torches.

You need the pirate captain's pickaxe to get the husks. (It costs 5 platina)
Mummies also sometimes drop them, which sell for a lot of gold.

This is the strategy I use to farm sandworm husks, I use the steam rifle that the steamlord drops.

This fight can kill you right quick, even with a potion of curse immunity, the Lamasu flies over the stage (that has spike pits) and shoots a lot of cursed bullets, on top of that, it summons Liches and small turrets, it gets chaotic really fast.

I was able to defeat it using the Necromancer's set and the steam rifle to destroy its armor.
Playing a wizard is not my style but I tried with the others and got annihilated.

Ranged didnt work because the Lamasu was too fast and I couldnt take out the liches fast enough, they would swarm me and Melee didnt work for me because if I got close and it released its bullets, a lot of the would hit me at the same time.

Dont destroy the turrets if they spawn away from where you are fighting, its one less lich to worry about.

I finally got it by just summoning skeletons, running away and hitting it while I could to remove armor.

Buy a large painting from the Mayor for 1 gold.
Before you place it, "Rotate" the painting using Q or E keys to change it until you see the one in the achievement icon, place it and the achievement is yours!

I found prize fishes at the lake at D3, no raining required, just luck and patience.
For the expert one, I spent hours fishing in a stream until I got it here:

Buy the 10G fish rod from the fisherman at town.