The problem is that it does absolutely nothing! This isn’t something that is even remotely obvious, because nothing in the game tells you this. And everything about the Brain Stone looks legitimate. It’s found inside a gift box inside Dalaam Palace. And its intended function is that keeping it in your inventory will prevent attacks that block your PSI from connecting. Basically Earthbound’s version of silence protection. This should work similarly to how the Franklin Badge works, in that just having it in your possession will reflect all lightning attacks.
How is the Brain Stone Supposed To Work?
Earthbound handles passive battle items by ‘checking’ for them in the code. If we go back to the Franklin Badge, this item will be assigned a number. Let’s say this is 1. If you then get hit by a lightning attack, the code will check for item 1. If this check is successful, the code will reflect the lightning attack instead. It’s similar to Pendant items, such as the Earth Pendant and the Fire Pendant. The game will check for these items, before bestowing the relevant PSI protection. Unfortunately the developers failed to apply this sort of coding to the Brain Stone. The code just isn’t there at all, or at least it doesn’t work properly. Absolutely nowhere in the game does the code check for a Brain Stone (yes, I tested this in-game). This means that this item does nothing but take up a space in your inventory. I don’t think this is intentional either. Earthbound has plenty of quirky and purposely useless items, so it wouldn’t be a surprise if this also applied to the Brain Stone. I just think the developers forgot to code it in! The best thing you can do is just to never pick it up in the first place. If you’re a completionist and can’t help yourself, then pop it into storage and never think of it again.
Enemies That Can Block PSI Attacks
Okay let’s say for argument sake that either you don’t believe me, or you’re playing a hacked version where the Brain Stone actually works. Getting your PSI blocked is actually a super rare occurrence in Earthbound. Only a handful of enemies have attacks that cause you to lose concentration – but even then they rarely use them and they are rarely successful. If your party gets their PSI blocked, their PP window is crossed out with a big X. This is naturally cured after a few turns though. Here’s a list of all enemies that can block your PSI:
