Chrono Trigger/Bosses

Yakra
See Chrono Trigger/The Queen is Gone

Dragon Tank
See Chrono Trigger/The Trial

Guardian
See Chrono Trigger/Beyond the Ruins

Sir Krawlie
See Chrono Trigger/Beyond the Ruins

R Series
See Chrono Trigger/The Factory Ruins

Heckran
See Chrono Trigger/The Village of Magic

Zombor
See Chrono Trigger/The Hero Appears

Masa & Mune
See Chrono Trigger/Tata and the Frog

Masamune
See Chrono Trigger/Tata and the Frog

Nizbel

 * Found: Reptite Lair - 65,000,000 B.C.
 * Charmables: Third Eye
 * Reward: 500EXP, 10TP, 0GP
 * HP: 4200
 * Strengths: None
 * Weaknesses: Lightning

Attacks

 * Releases electrocution energy.: Used a short while after being shocked with Lightning-based attacks. Does anywhere between 100-200 lightning damage to everyone.
 * An earthquake attack that does about 40 physical damage to everyone.
 * A ramming attack that does about 50 physical damage to one person.

Description
Not too hard of a battle. Start out with a good dose of Lightning to shock Nizbel, therefore lowering his defense. Then whack away at it. If Ayla has Cat Attack, use it. It's priceless. Otherwise, Rollo Kick will suffice. Eventually Nizbel will release his Electrocution Energy. That'll do about 100-200 damage to your party, so heal up and start over with Lightning, following up with high-powered attacks. Crono and Ayla's Drill Kick and Crono and Marle's Ice Sword work well, as does replacing Marle with Lucca and using Crono and Lucca's Fire Sword. Ultimately you will want Marle in your party, rather than anyone else, because Aura Whirl will be helpful in reducing time taken to heal up your party after Nizbel's electrocution attack. Nizbel will be cut down to size soon enough, and you can continue your journey. If you've boosted Crono's speed, you can probably keep casting Lightning without giving Nizbel any chance to fight.

Slash

 * Found: Magus's Lair - 600 A.D.
 * Charmables: N/A
 * Reward: 500EXP, 10TP, 1500GP
 * HP: 3200 (First), 5200 (Second)
 * Strengths: Water
 * Weaknesses: None

Attacks
First fight


 * Attack, attack, attack: Does about 90 physical damage to one person.
 * A close range fiery punch that does about 50 physical damage to one person.
 * An energy wave attack, which does about 60 damage to everyone.

Second fight


 * An attack which resembles Crono's Slash. Your opponent will position himself around the room so that it always hits at least two people, and does about 50-60 physical damage.
 * Yes indeed!: Does about 90-100 physical damage to one person.
 * A close range sword slash which does anywhere from 40 to 70 physical damage to one person.
 * A leaping sword slash, which does between 120-150 physical damage to one person.

Description
Never let anyone's HP fall below 100. (This is an arbitrary number for convenience.) Stick to attacks and physical techs. Use double techs as you desire, but don't bother if the dual tech damage is less than if both characters used single techs. Dedicate someone to healing. Frog's Heal heals all 3 party members, and if you equip him with Rage Band he can add to damage while healing full time. Give Crono the Silver Stud if you want him to use Spincut through the whole fight. Have Lucca cast Protect on everyone, which will mitigate Slash's attacks. You can succeed without Lucca, but this makes healing less important. At the end of phase one he will hit the entire party for low damage, so as long as nobody's HP is in a "blink state" you don't need to revive anyone. The second phase begins without giving you a chance to heal or use ethers. Slash will use more attacks, have more turns, and hit harder. This is why you don't want anyone's HP to fall below 100 in the first phase.

Make sure you pick up the sword when you win.

Flea

 * Found: Magus's Lair - 600 A.D.
 * Charmables: N/A
 * Reward: 500EXP, 10TP, 1000GP
 * HP: 4120
 * Strengths: None
 * Weaknesses: None

Attacks

 * Prism Beam ♡/Darkness: Damages the entire party (40-50 damage) and attempts to blind them.
 * Waltz of the Wind/Chaos: Attempts to inflict Chaos on one person.
 * Rainbow Storm/Wind of Poison: Inflicts about 50 damage to everyone and attempts to poison them.
 * The Stare/Flea's Magic: Turns one character on the others - inflicts 80 physical damage to everyone. Used as a counter-attack to any magical attack on Flea.
 * A sleeping bomb move which attempts to put one person to sleep.
 * A weak ranged attack which inflicts 40 physical damage to one person and may put the target to sleep.

Description
The first version of Flea is actually a Joker. One hit kills him, although he uses MP Buster as his parting shot. However, if you allow it to attack you first, and you're equipped with a Rage Band, you'll counter-attack it instead and it won't be able to use MP Buster. Now comes the real Flea. Not too difficult. Crono and Frog's X-Strike and Crono, Frog's and Robo's Triple Raid Triple Tech work very well here. Heal often, use powerful attacks and do it quickly, and you shouldn't have too much trouble. However, you will want to be quick about defeating Flea because he loves to use status-inducing attacks, e.g. Prism Beam/Darkness and Rainbow Storm/Wind of Poison and you will pretty much always get one person who gets inflicted with the associated status ailment. Flea's magical defense is also really high, and he has a pretty nasty counter-attack to it, so stick with physical attacks. Also, for some reason, Flea is less susceptible to physical attacks than Slash, but has less HP.

Ozzie

 * Found: Magus's Lair - 600 A.D.
 * Charmables: N/A
 * Reward: N/A
 * HP: N/A
 * Strengths: N/A
 * Weaknesses: N/A

Description
This fight is laughably easy. Ozzie encases himself in a shield of Ice. All you have to do is attack the switches next to him, instead of attacking Ozzie himself. Now sit back and watch the fun!

Magus

 * Found: Magus's Lair - 600 A.D.
 * Charmables: N/A
 * Reward: 1500EXP, 15TP, 3000GP
 * HP: 6666
 * Strengths: Variable
 * Weaknesses: Variable

Attacks

 * Lightning 2: Deals about 150 lightning damage to the entire party.
 * Ice 2: Deals about 100 water damage to the entire party.
 * Fire 2: Deals about 150 fire damage to the entire party.
 * Shadow Bomb: Deals about 150 shadow damage to one ally.
 * Dark Matter: Deals 250 shadow damage to the entire party.
 * Geyser/HP Down: Does about 70 damage to everyone.
 * A slashing attack which deals about 75 physical damage to one person.

Description
The toughest fight you'll have at this point of the game. Magus will routinely switch between Fire, Water, Lightning, and Shadow Barriers. Whenever a certain barrier is active he will only attack with that type of spell(level 2) and will absorb all magic not of that type. For example, a Fire Barrier means he'll use the Fire2 attack and only attacks with Fire magic can harm him. Because of this, hope that Magus chooses Shadow as often as possible, especially if you have Robo in your party. Shadow Bomb only hits one person so the damage is minimal compared to Fire 2,Ice 2 and Lightning 2. The Masamune will also lower his magical defence. A healer is very necessary for this battle. If you have Marle, then you can use haste(if you have it) which will greatly help in the battle, especially when he tries to cast Dark Matter. Try to bring a balanced party for attack magic, to ensure that you can penetrate most of the barriers.

Whenever Magus is hit with any attack, technique or magic (aside from Frog's Masamune), he will switch barriers alongside one of his elemental spells. His intermittent attacks aren't as powerful, but he can slowly deplete the party with his Geyser/HP Down attack. If you're finding that he's always of a barrier type that you can't get through, then hit him with something like Crono's Spincut to force him into changing his barrier (but be prepared for the accompanying magical attack).

When you see "Magus risks casting a spell" he's dropped his defenses and is beginning to charge his Dark Matter on your party to cause massive damage. Heal before and after this spell and hit him with your most powerful attacks whatever magic you want, since none of his barriers are active at that point.