To kill him.

I suggest spectre armor with mana flower,tons of mana potions,rage potion,wrath potion,magic power potion, bowl of soup,sorcerer emblem spooky wings, mana weapon of choice preferably homing. Flatten some land to run across,also I suggest frosts park boots. Make lots of asphalt blocks put them in a extremely long line you will also need gravitation potion.

Once  ready, fish with truffle worm and summon him.flip gravity often as  the movement falling is faster than his movement speed.kill him till he gives bubble gun as the bubble gun can do serious damage with a good setup it can do real damage when setup right 

Duke fishron stuff

Duke fishron,the hardest boss in 1.2.4 you need really good stuff to slay him.

Mushroom biome

Oh wait... You can verse over long distances with Terraria multiplayer edition...

How to make shroomite armor finale

And here you have you full shroomite set :) thanks for seeing my blog and also I play on Terraria PE

So sadly we can't verse over long distances.hope you have a great day!

How to make shroomite armor part 3

Okay,so you have your auto hammer. Place it somewhere and get mushrooms from your above ground biome.you will need exactly 810 mushrooms for the full set(1 helmet a chest plate and boots)when you have mushrooms,go to auto hammer and craft the shroomite bars with chlorophyte bars and mushrooms. Once you have 54 shroomite bars go to orichalcum/mithril anvil and craft the helmet you choose, the chest plate and the leggings/ boots.

How to make shroomite/mushroom armor part 2

Okay,so you will need to go underground to find mushroom biome,destroy mushrooms with anything but pickaxe/drill and after destroying many mushrooms you shall get at least 1 mushroom seed(you may have to wait for mushrooms to regrow many times and destroy mushrooms many times before you get 1 mushroom grass seed) plant the seed in your 200-400 mud block above ground biome and afk it will take hours and hours for it to grow. Then once you have your own mushroom biome make sure all your other npcs have houses,I forgot once and had to make many houses in mushroom biome.

Once you have gotten the npc with a mushroom on his head,you need to get 1 platinum coin.to buys the auto hammer.