Gazer can be a decently tough boss at this point of the game, but still quite manageable if one prepares. Its physical attack, which hits all party members, can deal moderate damage, depending on Defense, while Eye Beam can critically injure a single target, sometimes even kill with one shot. Hypnotize is its least threatening attack, as it has a high chance of failing, especially if someone has a Light Bangle. Needless to say, buffing and group healing tactics are highly advised. Have Ryu start off with at least two rounds of Shield to bolster the team, then you can transform him using Flame and Defender, though be wary of Hypnotize while in that form. If you opt out of using Accession, then have Ryu focus on healing the team with Vitalize (if he has it) and using physical attacks and/or Jump. Nina should focus on using Simoon or Iceblast, as they'll deal the most damage. Magic Ball, if she has it, is also highly recommended, especially combined with Meditate, which can deal close to 200 damage a shot with just one Meditate. If she knows Shield as well, spend a round or two using it for extra reassurance. Momo should use physical attacks and Quake while healing when necessary. If using Garr, stick to physical attacks, possibly combine them with Focus if he has it, which can deal close to 300 points of damage in one shot. If using Peco, use physical strikes. It's also recommended that you steal the Wisdom Fruit early, so Charm + Steal can easily nab it, so take a turn or two to do so.