http://i.imgur.com/rXyyVwD.png
Apparition is essentially immune to all physical attacks, is 'weak' to mental attacks, but has 4294967292 psy defence o.O
Though the other apparition only has 0 psy defence
Edit: it turns out psy attacks still hit it for normal damage, so not sure what's going on.
Its a 32 bit integer meaning either -4 or the number you see depending what meaning you put into the most significant bit.
Plainly said, it is a visual bug. Consider they got -4 psy defense, so psy attacks deal increased damage on them.
Quoteso psy attacks deal increased damage on them.
Nope! Psy defense has no influence on resistances, and never has. Psy Defense is usually used to determine how effective a character is at healing and protecting others. In previous games max health was directly tied to a character's psy defense, but never how well they resist mental attacks.
Ah! That's a quick fix; it'll be in the next update. Marking it resolved. :)