It can spawn after defeating at least one Hecteyes. There is a 10% chance Glaring Eye will spawn in six possible locations where a Hecteyes has been defeated. In the International Zodiac Job System Glaring Eye drops the Scorpion Tail.
Glaring Eye is not difficult when fought alone, but if other monsters join in the battle it can be very difficult. The Nihopalaoa trick should be used to defeat any other enemies that are interrupting the fight before killing this rare monster.