Hey! Just beat Eye of Cthulhu using these restraints, here's some info of how it went:

First Clear: Ranger using Shurikens. Theoretically one could use any ore bow too, but Shurikens worked great for piercing the several Servants spawned in the fight.
Other clears:
For mage, I ended up just going with the diamond staff/gem robe and Tim hat as well as Ninja pants for extra damage.
For melee, I did one run with Starfury (since that's unlocked with a kill of the Eye) and one run with Rally and Yoyo upgrades (since that's all accessible pre-boss).
For summoner, this one was hardest. So let's talk about it.

You only have one whip; Leather Whip. You only have two armor sets theoretically; Ninja armor for damage or Platinum/Gold for defense. You have an option of three summons though, being Finch staff, Abigail's Flower, and Slime Staff.

Realistically all you need is the leather whip to kill the eye; I did try that with full Menacing accessories and Ninja armor. However, the summons do help greatly, and reduce the boss time significantly as you have to focus less on the minions usually.

Between the Finch, Slime, and Abigail, the Finch is easily the best. It's fast and has the best flight. However, since it's world-dependent unless you use a quality of life mod to allow yourself to craft it, I opted not to use it. That leaves the Slime and Abigail.

Abigail, despite being able to infinitely pierce, sucks. She's slow, attacks slowly, and also doesn't like to travel far from the player. She works when you have to deal with the turnaround in your arena to deal with the several Servants that'll spawn throughout the latter half of the 2nd phase, though she'll almost never deal damage to the main boss, with the exception of if she happens to be close enough to it when it stops to spawn extra minions AND you last tagged the boss. So, slime staff it is, despite the rarity. Hey, at least you'll want to be grinding King Slime for crap tons of Souls anyhow.

So, you might ask yourself, is this unnecessarily difficult? And what does this bode for the rest of the challenge? I would honestly say it's definitely difficult, but nothing NEAR unnecessarily. It's doable, even without potions. Anyway, isn't that the moniker of a Souls boss? Sometimes your preferred weapon type or strategy will get you killed against that one boss. Summoner and the Eye is just that.

The other question is, what about the other bosses prehardmode for Summoner? Well... good news! There's a really cool event called the Old One's Army that grants you a TON of Summoner upgrades- namely sentries. It's locked behind the Eater of Worlds, yes, but that boss is also doable, if very slowly. As a matter of fact, the very first thing I'll fight Eater of Worlds with is Summoner, just to prove it.

(Post continued in next comment.)

(Continued...)

Lastly, I need to propose a couple changes. I'll edit the main rules each time I propose these changes, but I'll also write them here.

1. Added the Tinkerer Clause: No matter what stage of progression you are at, you are FREELY allowed to Reforge items from the Goblin Tinkerer. You are NOT allowed to merge accessories using the Tinkerer's Workshop until after you've defeated the Eater of Worlds with at least ONE class.
   
2. Modified the "Sky Items" lock to include Stars.
   
3. Modified the "Demonite/Crimtane Items" lock to include meteors.
   
4. Added a TOTAL weapon ban on Grenades, Bombs, Dynamite, Explosives, Fireworks, ALL Jousting Lances, and Molotovs. May add more soon.
   
5. Added rules that exclusively ban hoiks and teleporters from boss arenas.
   
6. Added a rule that allows traps in an arena Post Skeletron.

Now, let me just explain each of these, since some are self-explanatory and others aren't.

With the Tinkerer Clause,, the only reason this is added is because, simply put, any craftable item can just be rerolled at the shimmer for better reforges; and any droppable item can be farmed from enemies for the desired reforge. So there's no point in gatekeeping reforging from these accessories. Also, accessories that come from chests in the world, while predetermined and thus cannot be rerolled for better stats in any way, ALSO are allowed to be reforged, since it seems pointless to allow only some things to be reforged REGARDLESS if it skirts slightly around the rules a bit.

The inclusion to stars on the Sky items list is solely because of Jester's Arrows. These items completely trivialize the Eye of Cthulhu fight, whose main gimmick in For the Worthy is the EXTREME excess of minions. There are amazing piercing weapons in the shurikens and throwing knives, and also they clump together over time with a good enough arena and dodging. The bosses are still meant to be hard for a first clear, and I know ranger will be a go-to for most people due to its low investment. I don't want to also make it even easier than it already is.

Demonite and Crimtane also now banning meteorites is pretty much just because they spawn due to breaking Shadow Orbs/Crimson Hearts. So it just makes sense that way.

The weapon ban on Grenades, Bombs, Dynamite, Explosives, and Fireworks are solely because of the MASSIVE AoE damage they deal in both prehardmode and hardmode, and the variety of things they simply instakill. Which is just unfair to our lovely bosses. (Also, Bouncy Grenades having S tier scaling is WAY too strong, and instantly propels them into S tier weapons in the mod.) The ban on Jousting lances is similarly due to their insane damage, exploit, and instakill potential that they have over other weapons in specific scenarios, so they're discluded for that reason. For molotovs, it is solely because the shrapnel they create absolutely shreds all prehardmode bosses. As far as I'm aware, even weapons with shrapnel in hardmode don't decimate bosses there as badly as they do in prehardmode.

Rules against hoiks and teleporters, similar to the weapon bans, is just so you can't completely trivialize a fight with it.

Rules for traps post-Skeletron is solely because of the fact that wiring is locked behind the Mechanic; except you can find traps and wire setups naturally in the world, and Shimmering things for wires also exists. So, this just sets it in stone that you can use traps once you get CLEAR access to wrenches and the like, and NOT before it.

Welp, see you once I beat the Eater in my world!

Oh! I also just realized .Some people might freak out about the Boss Nuzlocke because you can't beat Skeletron more than once... normally. And so I remind everyone that the Clothier Voodoo Doll exists... just kill a Clothier with it equipped at night, and voila! Rounds 2, 3, and 4.

I need some clarification for a few things.
1. Are we allowed to use bombs as tools (aka digging out large areas) as long as we don't use them to kill enemies?
2. Stars. Can we use them for enchanted night crawlers and stars in a bottle, or are they banned completely?
3. Can we use the minishark? It can be bought by grabbing (but not using) the boomstick from the jungle and having the arms dealer move in.

Originally posted by TheSmolPopato:

I need some clarification for a few things.
1. Are we allowed to use bombs as tools (aka digging out large areas) as long as we don't use them to kill enemies?
2. Stars. Can we use them for enchanted night crawlers and stars in a bottle, or are they banned completely?
3. Can we use the minishark? It can be bought by grabbing (but not using) the boomstick from the jungle and having the arms dealer move in.

1. Ah crap, forgot to mention, the weapon bans list is solely for boss fights and events. You're free to use any of those weapons outside of progression locks in events and stuff. Thanks for mentioning.
2. Banned before your first EoC clear; you can easily clear Eye with shurikens and unlock nightcrawlers and stars in a bottle for all your other progression needs. Though that does remind me on the weapon bans clause, I probably should ban Jester's Arrows altogether due to their absurd DPS output especially against worm bosses.
3. Minishark is progression locked behind your first Eater/Brain clear, since the Arms Dealer can also move in from the shadow orb/crimson heart drops. So you don't need to kill Queen Bee at all, just Eater.

Adjusted the rules accordingly; thanks for mentioning these things!

How did you use the Starfury against Eye if all the chests in the sky islands are locked in legendary mode? Golden Keys are locked behind skeletron due to being in the dungeon.

Also, should the star cannon be banned? It's unlocked after beating eater, and while stars are generally hard to get, it can absolutely shred bosses, even in hardmode (like the destroyer). I think the fallen star costs makes it balanced, but you're the rule maker.

Originally posted by TheSmolPopato:

How did you use the Starfury against Eye if all the chests in the sky islands are locked in legendary mode? Golden Keys are locked behind skeletron due to being in the dungeon.

Also, should the star cannon be banned? It's unlocked after beating eater, and while stars are generally hard to get, it can absolutely shred bosses, even in hardmode (like the destroyer). I think the fallen star costs makes it balanced, but you're the rule maker.

You can fish for Sky crates. Fishing grants you so many upgrades pre-hardmode that help in bosses significantly. Just, fishing loot follows same restrictions as always (so you can't fish for thee ingredient you need in Summoning potions until post Queen Bee, since that requires jungle fishing, for example.)

And yeah, Star Cannon should be banned. I will also add that to the rules.

Originally posted by BosoBr0:

Star Cannon

Speaking of this... you can't even really use the Star cannon or Super Star Shooter... at all. Since the bosses reflect projectiles in Legendary FTW. So, it's banned just because I'm sure if it's traveling enough the reflection would bounce it back and forth in the boss, but still- in most normal circumstances it still wouldn't work even if it wasn't banned.

Few things.
1. Eye of cthulhu with leather whip is very doable, with golden armor and a mix of defense and damage reforges. Also finch staff can be obtained in any world, because you can shimmer the living wood wand into it. Living wood wand has a .33% chance to drop from shaking any forest tree.
2. Old one's army. Is it unlocked after beating the eater/brain ONCE with any class, or only after it's been beaten with ALL classes? I'm guessing it's only one kill, since you unlock combining accessories after one kill, which is locked behind goblins.

Originally posted by TheSmolPopato:

Few things.
1. Eye of cthulhu with leather whip is very doable, with golden armor and a mix of defense and damage reforges. Also finch staff can be obtained in any world, because you can shimmer the living wood wand into it. Living wood wand has a .33% chance to drop from shaking any forest tree.
2. Old one's army. Is it unlocked after beating the eater/brain ONCE with any class, or only after it's been beaten with ALL classes? I'm guessing it's only one kill, since you unlock combining accessories after one kill, which is locked behind goblins.

1. Ah, I completely forgot about that fact... then again I rarely use Shimmer to begin with so I know almost nothing about it still. Still, definitely doable.
2. As for that rule... I might reconsider changing it. Since I now reread what I wrote and completely missed the mark in what I interpreted between things- the Goblins Tinkerer is currently 'beat EoW with one class', whereas Goblin gear/Old One's is 'beat EoW with all classes' which sort of clashes.

I personally don't know whether I should make it be before or after, but then again Legendary mode EoW is... proving rather difficult as summoner, and so the additional summoning gear Old One's Army provides might be... pretty much the only feasible way to make the fight plausible.

But I'm still testing arena designs, so I still don't 100% know yet. I'll come back to this on Thursday, since I just got out of a massive shift at work today and have another massive shift tomorrow, and will have more time to actually do attempts on Thursday.

For now? Interpret how you wish; no penalty if things change later. It's your challenge anyhow, if you choose to do it.

Were you able to get a slime staff? I've killed king slime nearly 40 times and haven't gotten a drop. How long did it take you? (side note: I'm already at level 75 ;-;)

I beat EoW with summoner. I used platinum armor, all warding accessories, Leather whip and Vampire Frog Staff. the frog staff isn't hard to get, and will wreck EoW, it was about a 9 minute fight.

Also, should the Zapinator be banned? It's kinda broken, but also is entirely rng dependent on whether you get one or not.

Originally posted by TheSmolPopato:

Were you able to get a slime staff? I've killed king slime nearly 40 times and haven't gotten a drop. How long did it take you? (side note: I'm already at level 75 ;-;)

Oh, I found a slime statue underground with a natural wire and, since you're allowed to use natural wiring for things outside of boss arenas pre-Skeletron, I just set up a hoik and pressure plate and AFK'd overnight. Had like 60k slime kills and 7 slime staves, as well as a ton of gel.

Originally posted by TheSmolPopato:

I beat EoW with summoner. I used platinum armor, all warding accessories, Leather whip and Vampire Frog Staff. the frog staff isn't hard to get, and will wreck EoW, it was about a 9 minute fight.

Also, should the Zapinator be banned? It's kinda broken, but also is entirely rng dependent on whether you get one or not.

Oh, I totally forgot about Vampire Frog staff! I was just about to get on to test things today, so that's a good thing to know too. I just suck at dodging so I'll have to get into the rhythm of it again :P

I should make that ban though, now that you mention it. Also, I'd probably ban Space Gun+Meteor Armor combo, but either one is fine on their own. Just because infinite mana magic weapons are absolutely busted.

Editing the rules now real quick.