There are nine initial bosses in Dragon's Crown you must defeat before you can unlock online multiplayer. Some of these bosses are easier to combat than others. If you have a well-rounded party, you should do well against most bosses. Some are easily defeated with ranged attacks, while others are weak to aerial attacks. Each boss much be approached in a unique way to avoid taking damage, but it's possible to defeat every boss and obtain the bonus for not getting hit.
Read Prima's Dragon's Crown Beginner's Tips for even more strategies.
Stage: Ancient Temple Ruins
The Harpy only has a few attacks, most of which hit in front of it. Stay behind the Harpy to avoid a vast majority of its attacks. When it takes flight and dashes back, be prepared to evade as it dives toward your party. If you're playing as a Dwarf, you can pick up the boulder on the right side of the nest and throw it at the Harpy for considerable damage. Doing this also keeps you at a distance, which prevents the Harpy from hitting you with most of its attacks.
If you find yourself in front of the Harpy, do not stand close to it. If you do, it may grab you and inflict moderate damage. In addition, it has a multi-hit attack with its claws that can also cause considerable damage. Even if you're in front of the Harpy, if you stay in the air, most of its attacks will not reach you. Watch out for the feather shot, as it fires three feathers at various heights, multiple times in a row. Avoid these attacks, stay behind the Harpy or in the air and you won't have much trouble.
Boss: Doom Beetle
Stage: Wallace's Underground Labyrinth
Unlike some of the other bosses, staying in the air when fighting the Doom Beetle will only get you so far. However, this is a good tactic if you are not playing a class that has ranged attacks. If this is the case, use your aerial attacks, but evade if you see the Doom Beetle move at all. Most of its attacks will hit aerial opponents, especially when it jumps. Do not stay on the ground near the Doom Beetle, because many of its attacks have a wide range and will hit you if your character is anywhere close to it.
Your best bet is to use ranged attack classes such as the Elf, Sorceress or Wizard. If you choose the Amazon with some of her invincibility skills, she also does well in this battle. Even using a ranged attack class, be careful if the Doom Beetle flies back or jumps into the air. The stomp that occurs following the jump can inflict significant damage, and if it flies back, it will lunge towards you from across the screen.
One of the most important aspects of this battle is to take down the grubs when they appear and enter their cocoons. If you don't take these down quickly, they will turn into weaker versions of the Doom Beetle.
Stage: Forgotten Sanctuary
To defeat the Golem, you must first acquire your own. Activate the runes just beyond the second stone Golem to animate it. Once it's animated you must fend off attacks from the front and back of the Golem. Defeat as many enemies as possible as your Golem slowly makes its way toward the other Golem. It's important to catch the goblins before they get close to the Golem because their bombs inflict more damage than most other attacks.
Once you reach the Golem boss, you still need to protect your own Golem. However, you also need to go on the offensive. Defeat any goblins you see and grab the bombs they drop. Toss the bombs at the feet of the Golem to inflict damage. When the Golem reaches its sword, move behind your Golem until it swings to avoid taking damage. There are other safe spots behind the Golem boss and in the foreground, but they're not as safe as simply standing behind your Golem. If you protect your Golem long enough, it will bring down the boss Golem with relative ease.
Stage: Ghost Ship Cave
This is a unique boss because it's a horde of pirates. Fight the pirates as you would any normal enemy. The only trick to this battle is the magic lamp. When it appears, make sure you grab it as quickly as possible, then call forth the genie to assist you in battle. If one of the pirates picks up the lamp, attack him to knock the lamp from his hand, then pick it up yourself. If you allow a pirate to hold onto the lamp, he will call forth the genie that will unleash his attacks on your party. You can knock the lamp out of a pirate's hand at any point, even after he's called the genie.
Stage: Bilbaron Subterranean Fortress
The only important strategy to note about fighting the Minotaur is to never stand in front of it. No matter how far away you may be, never stay in front of it or in line with it on the screen. It has attacks that will reach all the way across screen and they hurt quite a bit. Stay behind the Minotaur at all costs, but don't worry about being airborne. You can fight it very well on the ground. As long as you stay behind the Minotaur, the only thing you really need to worry about are its jumps. If it jumps, dodge away from it, then move behind it again and resume your attack.
Stage: Castle of the Dead: Catacombs
There are several vampires you must defeat when you engage this boss. If you've entered all of the rooms on the way to the boss, you'll also have three girls to protect in addition to defeating the vampires. If you have a Fighter or Sorceress, it's fairly easy to protect the girls. Simply use the Fighter's Cover Allies and Distraction skills, or use the vertical tornado attack as the Sorceress. If you're not playing either of these classes, just stay close to the girls and fight off any vampires that appear near you.
When fighting the vampires, try to stay behind them unless you're protecting the girls. All of their attacks are forward facing with the exception of their projectile attack. Evade to avoid the projectile unless you're protecting the girls, at which point you should take the hit. If the vampires take flight, continue to stay behind them, but use aerial attacks to bring them back down to the ground.
Defeat all of the vampires and the narrator will state that the girls have been turned. It's important to note that he is not referring to the three girls you saved. He is referencing the other girls in the catacombs you did not come across.
Boss: Wyvern Leader
Stage: Old Capital
The best way to defeat the Wyvern Leader is to stay behind it as much as possible. It does not have any attacks that will reach behind it. When it takes flight, remain behind it and use aerial attacks until it lands. If it darts across the screen, you will dodge this attack automatically if you're behind it when this happens. Follow it to the other side of the screen and reclaim your position behind the boss. When it summons another wyvern to assist it, ignore that and let the other party members take it down.
Stage: Mage's Tower
The Warlock hovers in the air throughout most of the fight. Use aerial attacks to keep yourself in the air and attack the Warlock as long as possible. The orbs circling the Warlock indicate which magic attack he's about to use. If you're in the air, only the green orb is something to concern yourself with. If the Warlock is using this orb, move away from him as quickly as possible until he changes orbs. If you've got ranged aerial attacks, those work best against this boss and allow you to avoid almost all of his attacks.
Stage: Lost Woods
The Gazer is one of the harder bosses in the game. The best strategy is to use a class with ranged attacks. The Wizard, Sorceress or Elf are very well equipped to handle this battle. With one of those classes, stay as far away from the Gazer as possible and attack from a distance. If the Gazer teleports, move to the other side of the screen and continue your attacks. The Gazer only has a few attacks that reach across the screen and they're easy to avoid.
If you're not playing a class that has a good ranged attack, stay in the air as much as possible as you battle the Gazer. If it begins to puff up, get as far away from it as possible. This is the precursor to the Gazer's most damaging attack, a series of beams the shoot from the ground and inflict massive damage to anyone in your party that gets hit.
Try to stay behind the Gazer as much as you can. It has attacks that reach behind it, but not all of its attacks are capable of this. When it engulfs the ground in flames, stay airborne for as long as you can. If you have to land while the flames are still lit, move away from the Gazer, then land.