What is the easiest most efficient way to farm Shadow Scales?

The Eater of Worlds is the only way to obtain Shadow Scales, but don't worry; it's arguably the easiest boss in the game because each section of its body gives you a heart upon being destroyed.

You don't always get rotten chunks or vile powder from killing corrupt enemies so the best way to farm the eater of worlds' shadow scales is to destroy a heck load of shadow orbs. You have to destroy three orbs to summon him once.

One easy way is if you have the Demolitionist NPC, you can purchase bombs and blow up Ebonstone to get to Shadow Orbs. Not only can you get a musket (which allows access to the Arms Dealer), sometimes a meteor will land. The Eater of worlds will also spawn so if you don't have worm food you can just break shadow orbs with a hammer. Every 3rd Shadow Orb that you break will spawn the Eater of Worlds.

Actually, there is another way to get Shadow Scales. Fight a bunch of Eaters of Souls (you will obviously get some armor in the process) approximately 10000, and I don't know about you, but I got a Shadow Scale. Just saying. I play on mobile.

kill the eater of worlds a few times. To kill the eyeball silver armor and a gold sword should do it.

i killed him using a lights bane and iron armor with some potions to heal and a demon bow with fire arrows. he is not to hard, you just need to keep track of how many there are (if you hit him in half),so that you don't get hit by a lot of smaller ones. if you can kill the small eater of worlds, then it is not hard because he does not do to much damage. i killed him and got 118 demonite ore and a bunch of shadow scales. if you kill the eye of Cthulhu first, and then use his drops to make a lights bane and demon bow. ( make the demon bow first, and then use it to kill him again,so you can make a lights bane) he is not a hard boss if you have potions of healing and a o.k armor. (iron or greater) i had only 120 hp when i killed him and it is not hard to spawn him if you have the driad npc because you can buy the purification powder and use that to destroy the orbs. PS, meteor armor and weapons is worse than demonite Armour and weapons.

The easiest way is to go destroy some shadow orbs (three should do) and defeat The Eater of Worlds.
The Eater of Worlds should drop some shadow scales.

I found it fairly easy to use a Vilethorn which dropped on the 3rd shadow orb I destroyed. It was very useful.

The only way to get shadow scales is by defeating the Eater of Worlds. Here are some strategies to defeat him:

• Defeat the Eye of Cthulhu by crafting a Suspicious Looking Eye at a demon altar(takes 10 lenses from Demon Eyes). Using this item will spawn the Eye of Cthulhu and when you defeat him(suggest using lots of flaming arrows with the best bow you have), he will drop Demonite Ore. You can use this to craft powerful weapons.
• You can also mine to find Demonite and other ores to craft more powerful weapons and armor, etc.
• Adventure in the corruption. If you mine in the corruption(do not suggest until after you have defeated the Eye of Cthulhu and gained more equipment) you will find Shadow Orbs. Smash these with hammers or explosives(from pots and the Demolitionist NPC). The first one you smash will give you the Musket and 100 musket balls. This is a good weapon at this time in the game and will allow access to the Arms Dealer NPC. Smashing more orbs can give you powerful weapons. However, every third orb you smash will spawn the Eater of Worlds.
• If you are lucky and get the Vilethorn from a Shadow Orb, it's great against the Eater of Worlds.
• You can also spawn the Eater of Worlds using Worm Food. This is crafted using 30 Vile Powder(crafted from Vile Mushrooms found in the Corruption at a placed bottle/alchemy table) and 15 Rotten Chunks, a common drop from Corruption enemies such as Eater of Souls, at a Demon Altar.
• If you plan to use Worm Food, make a large platform above ground to fight on.
• Summon the Eater of Worlds. Using the Vilethorn, Musket, demonite weapons, etc. and good planning, you can probably defeat him first try. If not, his body sections will each drop some demonite ore and shadow scales that you can use to craft the Nightmare Pickaxe, Shadow Armor, and other things.
• Once you have decent enough equipment, you can farm the Eater of Worlds for lots of money, demonite ore, and shadow scales.

Good Luck!