Eater of Worlds can be a tough boss to beat, even for intermediate players. Caution should be taken for battling it.
Arena preparation is mostly not needed for this boss, although for weaker players a platform can be constructed overground.
Meteor Armor is recommended for the fight because of the high defence and the good bonuses that the player gets from them, although the player can use Gold Armor as well, but in that case 350-400 Max Health is recommended.
For melee users, War Axe of the Night or a Phaseblade are valid options. Light's Bane is also good but deals significantly less damage than the War Axe or the Phasesaber. A Blue Moon is also a great choice as it can damage multiple sections of it at once.
For ranged users, Demon Bows are a good option, Ammo like Unholy arrows makes the fight easier. With meteor armor, a space gun can also be used.
If the player has access to the Underworld Shadow Chests, weapons like Sunfury or Fire Flower can make a huge difference. Also for players with many fallen stars, Star Cannon is an ideal option.
A shackle is a good choice that provides extra defence. For surface fighters, spectre or rocket boots can be used for extra mobility. Other speed objects like Anklet of the Wind are also useful for Platform Mobility.
Healing Potions are recommended for this fight (as with most boss fights). Other options like Swiftness, Hunter and Night Owl are also valid for extra advantages. An important choice is also ironskin.
The Fight Edit
For players with fast weapons, and enclosed area works best. For this technique, though, good armor is recommended. Just sidestep and whack away at the boss, and if using ironskin, you will barely take significant damage.
For players with skybridges, it is good to keep ranged weapons handy as if the boss is out of melee range, then there is a second option.
If these steps are followed, the boss should be pretty easy to beat.