I don't remember ever encountering an intangir, but I do remember zone eaters. Maybe in the PS1 version it's different..

@ Raziel about evilmask. Just cast spells on yourself, and they reflect off you onto the evilmasks.

My most annoying enemy would have to be that guy at the top of the tower in FF6, the one that casts ultima when he dies. He was really hard and annoying..