Or you can use the super-cheater method that I like: Get all your characters up to lvl 30 before the fight with Yaridovich! There is a Dry Bones in the room with the shopkeeper in the Sunken Ship (The room right before the bottom half of the door puzzle) attack it and, giving Mallow as much speed as possible (43 is usually good, use Zoom shoes and ... I can't remember the item giving 15 speed) and use Thunderbolt on the enemies. At a high enough magic lvl, you will wipe out every enemy in 1 hit, gaining 27 exp easily. Give someone the Exp. Booster for double exp! Do this for a loooooooooooong time until you hit lvl 30, and the shopkeeper is right there for your items! Then Yarid (and everyone else, for that matter) goes down real easy!
If you don't have the bile for that, you definatly need Toadstool in your party. Yarid's attacks do 50-70 damage to all members at once. Group Hug erases that leaving your other 2 members (I recommend Mario and either Bowser if you want a higher hit or Mallow if you want to ditinguish the clones; Thundrbolt does 350 or so damage to the fake Yarid and about 2 damage to the real one.) And don't forget Pick-Me-Ups either, of course, I beat him without using an item once lol. (Sorry, I had to say that.)
------------------------------
What? Someone made a really dumb comment? This looks like a job for...
CYNICMAN!!!!!
That''s right! CynicMan, protector of tactlessness, enforcer of raw, abusive sarcasm!
Cynicman: What kind of introduction is THAT? It''s not even a sentence!