I haven't had much free time to checking out the Christmas/general holiday celebrations that've been going on in Ragnarok Online and elsewhere. What I've read at the iRO news is that Antonio's no longer showing up across Midgard, but rather in the boonies of Lutie.

I'm not sure if I read that right, though, or if he's still showing up elsewhere.

Maybe we've finally put a dent in the Antonio crime ring!

I don't know if it's still explained in-game, but the story behind Antonios is that they're rejects from a Santa Claus academy that want to ruin Christmas for everyone since they couldn't make the grade. If you listen closely when you knock one out, you'll hear more than just the grunt they make as they're pulled into their black—er, red bag of tricks.

Right after the grunt, you'll hear this "FLUMPH-
WUMPH-RUMPH" like watery sloshy noise.

It really does sound like those Antonios carry around a giant tank of water in their bags. Or maybe something in the bags turns them into Tang. I wouldn't be surprised!

Of course, there's always that giant black hand-thing that the Antonios use to attack. Maybe it's some kind of liquid shadow like Eddie from the Guilty Gear series? Wait, shadows aren't liquid ...

Bah! If they can create liquid smoke, they can create liquid shadows!

Also, this is totally why you shouldn't disturb an Antonio after he's taken refuge in his bag.

Christmas tree surface to air missiles. The ornaments are frag grenades! Quite nasty.