ruby is much easier than everyone thinks.i do not know why no one here know about this,but use dazers (item) on it and it will stop.

at the beginning of the battle,kill two people in your party.when ruby digs its hands into the ground,use phoenix/life/phoenix down/whatever you want.

then use dazers on it immediately.when the stop status wears out,use another one.attack when it is stopped.use cure/heal/remedy/whatever recovery you want when necessary.

try it.ruby=pawned really really REALLY badly.

btw,dazers can be obtained from one of the enemies in city of the ancients,i just forgot which.

i mean you really have to try it.