idk what manamon to use, but if you want to capture him you need to get him paralized, and keep using soul split untill he has 1% hp i think pandorbit has soul split. then capture him with a net or kill him if you want.

soul split thus not effect erodiom

oh, i' no. sorry.

Hey there! This is a few manamon I would recommend:
Polosses: Ice is, as you already know, effective. Put the ice Dagger on him as well to get a little extra punch.

Pandourbit: Leonatar also works, but this guy has got the move unending curse, which will do around 35 damage to Irroadium every round. That'll shut down his healing pretty good. He only heals 29 HP per round, remember, so that's gonna help a lot.

Miterosier: He may seem weak at first, but once he learns white lance, he's great against Irroadium. Give him some power potions in the battle to pump up his attack even more, and make sure to use train points. divine protection is also a neet move.

Grandlan: This one's got Meteor Rush, which is great. Make sure to start pumping up his special attack stat early and giving him a few charmed potions during the battle. He also has copy, and make sure to use that, if you can, when Irroadium uses a move called magic dragon. That'll do a lot of damage to him, because he's weak to both magic and dragon. Tunnel is also nice, because you can use it every time he uses an oblivian move, which will happen every 3rd round. You can avoid final oblivian that way.

Mondevol: Both stun volt forparalysis and aura master for damage is good on this guy. He has a lode of HP as well.

Dramagon: With generally good stats all over, as well as moves like draco breaker, which does a shitlode of damage, and rehydrate for some healing every round, this guy is really good.

Oh and before I forget, Jayde's manamon guide has a lot of tips for this battle. Go check that out, if you haven't already.
Thanks, and hope this helped a little.

Squarpha is kind of bad. Not awful, but not great. Meh stats and meh moves, a neat ability that relies on luck to let you dodge a bit more than usual.

Unless you got rid of both Pandourbit, there's no reason you shouldn't be able to get yourself a Mutmo. Oristar is pretty frail, actually, but it's also super-fast. Wouldn't necessarily take it to a battle against Irroadium, but you might be able to pull it off.

and don’t forget palses.  I know my spelling is bad. but anyway
try to get him in     level      60 and he will be  really  powerful

Enchandithol and Oristar aren't ice types. They're magic types.
Prefer Grandlan, myself. It's much more versatile. Mondevol is also pretty good. Doesn't hit insanely hard, but it's a freaking tank. Lots of HP and decent defenses.

The thing with Irroadium is that if it wants to hit something on your team for super-effective damage, it's probably going to have the tools to do it. Your aim is to drop as much damage on it as you can. Paralysis is a very good idea, and confusion isn't terrible either. If you can drop both on him and then start wailing, you might get lucky. Getting three turns to its one is definitely helpful. Just don't have an entire team weak to flame or earth, since he has moves that will hit the whole field.

I still don't like this battle, even after almost three years. There, I said it.

Unfortunately, I did kill both pandourbits, simply because I failed to watch the enemy health and gave up chucking nets. Same thing almost exactly happened with the first two mythicals I came across, I went after them with type effective attacks and not enough nets. where can I catch a gremlin?