Once you have finished the first half of the game by playing each of the nine levels one time (the ninth is the Lost Woods), the second half of the game kicks in. A second path through each level - the (B) route - becomes available and you need to collect nine talismans by defeating the new bosses at the end of each (B) route. This trophy is awarded when you have collected all nine, and is an unmissable part of the game progression, as well as being the last step before you can challenge the final boss to beat the game (on normal difficulty).
The nine (B) routes can be tackled in any order (though if you extend you will move through them in map order), but some levels are definitely easier than others. On the map screen you can see what the level of the boss is, and this level will also generally be the level of all regular enemies on that route as well.
It is worth noting that generally speaking there are multiple ways to complete the B route to each level (though the levels still are linear), only some of which will net you the talisman. In some cases you get two chances to defeat the boss, and also there will be some sort of option to run away from the boss or alternately a non-obvious time limit to the boss fight. If you reach one of these conditions, it will on the results screen say something to the effect of 'You found the (levelname) exit' and the narration will usually suggest that you did not defeat the boss or the boss is still alive, whatever. For purposes of this solution I will call this sort of finish the ‘C route’ or ‘C exit’ (as in 'crap, no talisman').
I will list the bosses that need to be defeated as well as battle flow tips (exact strategies will depend heavily on the class you are playing as) as well as the talisman attained, in the boss level order (which pretty much corresponds to the talisman difficulty), but feel free to just fight these in map order with extends if you feel strong enough:
Ancient Temple Ruins, Green Talisman, Lvl 18 Medusa:
You will meet the medusa very quickly on the B route (third screen), you have the option to defeat her here, she is definitely the easiest of the bosses. The key attacks to be aware of are her petrify attack - face away from her when her eyes glow yellow, and the snakes that she calls which will tend to try and immobilize you if they touch you, which will open you up to either be hit by Medusa’s strong claw attack or leave you unable to turn away from her petrify attack. If you duck away from her in the first fight you will proceed through several more zones of level and eventually run into her again in her lair. If this fight goes on too long (2-3 minutes?) she will retreat and you will get the 'C' route. In practice she is pretty simple and there is no reason to not just beat her the first time you face her on the bridge.
Wallace's Underground Labyrinth, Aqua Talisman, Lvl 20 Cyclops:
As you walk onto the screen with the Cyclopes (plural of Cyclops - there are two), you will see a dead adventurer and a key. Pick up the key (Triangle button) and rush over to put it in the keyhole (push square while holding the key) and the key will start turning very slowly lowering the door. Now what you need to do is fight off the two cyclopes that are out, while allowing the door to close. Periodically, a cyclops hand from inside the prison will reach out and grab the door to stop it from closing - you need to hit and destroy this hand quickly or else it will knock the door back all the way up (typically this will happen 4 times). After a few minutes the door will shut all the way and you need to finish off the remaining Cyclopes that are out to earn the talisman. If the door is mostly open (not sure exactly but i think about 1/2 to 3/4th open) and you defeat a cyclops, then another will show up to take its place. If you take too long at shutting the door (mainly by letting the cyclopes keep opening it back up) then eventually the door will shut quickly on its own, but you will get the C finish for the level.
Bilbaron Subterranean Fortress, Orange Talisman, Lvl 22 Gargoyle Gate
When walking across the rampart area with the fireballs raining down on you, watch for the visual cue that shows up on the ground before a fireball strikes to help you avoid them. The Gargoyle Gate is a fairly easy boss fight, if you play along with the script and use the cannon mainly to damage it. When you first get to the gate you will have no great ways to damage it and you should focus on just defeating the orcs and goblins. Sometimes the goblins will drop bombs or crossbows, you can use those versus the gate (especially the bombs) and just generally to use them up so the goblins can’t use them against you. Shortly into the fight the knights will wheel out a cannon which you will need to first load a cannonball into (pick it up with triangle then face the cannon and use square), and then pick up a torch and light the cannon (hit it with torch). The cannon can miss if the gate is open at the time that it fires, so be aware of the gate position as you fire. During this time the enemies will be trying to destroy your cannon (similar to golem fight from Forgotten Sanctuary A route), so you will want to work fast. If you are playing solo or with AI companions you will have to do everything (load+light) so you really don’t have time to worry much about the enemies, obviously with a team of humans you could divide up the work (the battle is easy enough that it is not really necessary). If/when your first cannon gets destroyed, the knights will eventually bring you a new one after a time, or if the gate is low enough in HP you can finish it off yourself (smash attacks or weapons esp bomb works decently). I believe that after the second cannon is destroyed you run out of time and will end up with the C finish (need to go back and check this).
Lost Woods, Black Talisman, Lvl 23 Killer Rabbit
The rabbit is very dangerous at close quarters (“Run away! Run away!”), he can do lots of damage and can cause stun locks, especially to AI allies (he has a vicious streak a mile wide). Also he has a pretty difficult to avoid whirlwind attack (try and stay on the ground and run away from it – remember to change horizontal planes). Finally he has an attack that he may tend to use at low health which will one-shot anything it hits. If you take too long in fighting him some knights will show up to help you out, and eventually there is an exit that open up that you can run away from the battle (C exit). My focus in fighting him (esp if soloing) is to try and stay away from him as much as possible and then move in with the strongest possible attack and then quickly retreat. Unfortunately the Holy Hand Grenade of Antioch is not available for this fight.
Castle of the Dead, Yellow Talisman, Lvl 25 Wraith
When you first meet the Wraith, he is invincible. Quickly attack the door on the right-hand side of the room to smash it open and duck into it. Now you will be in a chase scene fleeing the Wraith. At intervals there will be goddess statues that you need to ‘light’ with a torch (hit it). Once this is done the wraith will be vulnerable until the statue is destroyed. Focus fire on him as fast as possible, for the wraith and the undead minions he calls will make quick work of the statue. If using human allies you can probably coordinate to both attack the wraith and defend the statue, but when soloing or using AI allies it just isn’t really much of an option, I found just wailing on the boss the best option (try to avoid the grab attack from the zombies – this wastes precious time). Once the statue is destroyed keep running and you will come across another statue and repeat. After two statues you need to zone and you will continue the fight with more statues on the next screen. I’ve never had the battle extend past the third statue, but I suspect that eventually (4?) you run out of statues and have to settle for a C finish (need to confirm this).
Ghost Ship Cove, Red Talisman, Lvl 26 Kraken
You get two shots to fight the Kraken. First chance you are on a ship and there will be kraken tentacles on each side, as well as cannons. You load the cannons with the crates of cannonballs and then you have to fire the cannon by hitting it with the torch. AI allies will load the cannons but will not fire them for you. Periodically a tentacle from the right side will grab the mast of the ship and start draining HP - you need to immediately attack that tentacle (use air attacks). If ship HP bar reaches zero then you wreck, whereas if you last long enough (or maybe destroy enough tentacles?) you will sail off into the mist. Either way you end up in a watery grotto, but if you survived the ship fight, there will be a chest, whereas if you wrecked I believe there are more foes to fight. Next you move into the kraken's grotto to fight him directly. First off note that in the background you can see three tentacles wrapped around three pillars in the cave – this gives you a visual indication of how much time you have to defeat the kraken to avoid the C ending. Over time the kraken will destroy these pillars, once he destroys all three the cave collapses and you exit the level. When the kraken first spawns he has two targetable tentacles in front of him attacking you. While these tentacles are up the main kraken head cannot be harmed. You need to defeat first the tentacles (this will spawn some lizardmen to charge you from behind) and then wail as hard as you can on the main boss. Eventually the tentacles come back (watch for a large wave attack that will hit you for big damage and possible stun unless you jump into the air), and you will have to repeat. If you defeat the Kraken before he collapses the cave you get the talisman, otherwise if the cave collapses you hit the C exit.
Mage’s Tower, White Talisman, Lvl 27 Chimera
The B route has a magic carpet ride (‘SFC’ runeword) and eventually you will reach the top of the tower and have to fight a chimera boss. As is traditional, the Chimera has three heads: lion, goat, and snake. The lion head mainly uses fire and bite attacks, the goat head uses support type magic and ice magic, and the snake head will spit poison at you. While you can attack any head, only the lion head makes progress towards defeating the boss, the other heads have individual hp bars and when this is depleted it will stun for about 30 seconds before returning to the battle with full HP. Therefore you want to focus most of your attacks on the lion’s head. The time limit for this battle is that over the course of the battle the chimera will smash the floor dropping you both down successive levels of the tower. The narrator will warn you about 15-30 seconds before this happens. Note that the Chimera will be a mirror image (ie lion head on opposite side of screen) when you resume the fight one floor down. You need to beat the Chimera before he smashes out the floor a three times, if you fail to do so you will reach only the C exit.
Forgotten Sanctuary, Blue Talisman, Lvl 28 Arch-Demon
It is sort of a toss-up whether this or the chimera fight is more difficult (arch demon has more dangerous attacks, but chimera fight is much more hectic and easier to bump into the time limit), but I put this one as the penultimate difficulty merely based on the displayed level. On the B route eventually you will reach a glowing summoning circle on the ground, which when stepped into will take you into hell (if you initially sidestep this circle you can destroy a statue to reach a room with a rare chest). After fighting a few demons you will quickly reach ‘the king of hell’ (who looks almost exactly like diablo from the popular series of action RPG games – I doubt that is a coincidence). This is I think the only example of a mid-boss in this whole game. Once you defeat him you will be ejected from the portal and eventually continue on to reach the Arch Demon. The Arch demon is a pretty tough fight, working a lot like a more difficult version of the Gazer boss (teleporting boss, lots of different attacks with visual cues), fortunately lacking in the magic-nullification ability, but unfortunately hitting very hard. Your best bet is to get good at identifying the visual signifiers of his attacks, and do a lot of dodging and hit and run with hard strikes when you get an opening to hit him.
Old Capital, Purple Talisman, Lvl 30 Red Dragon
Red dragon fight is hands down the most difficult of the regular level boss fights in the game (ancient dragon of course is harder). When you first meet him he will be in his treasure room and it is very difficult to maneuver without getting hit by his breath, claw, and fire attacks (and the tons of fire on the ground). Though if you are fairly over-leveled or have good close quarters fighting skills it is definitely quite possible to defeat him here, probably only with dying once or so. You can stack the odds in your favor by setting up a bag with all the +dmg to/-dmg from draconic enemies, fire resistance items you can find (immunity to burning is also great but tough to find). If you do not want to defeat him in this room, you can have Rannie open the door on the right and switch the fight to a side-scrolling ‘escape’ type mode. The dragon will chase you until you get to a crate, which will have a great shield in it – open the crate right away but do not pick up the shield. Fight dragon (he will mainly use claw attacks and fire breath) until you hear the narrator give an audio cue that he is about to unleash his breath attack. At this point quickly pick up the shield and you will be able to avoid damage (you just stand still, there is no button to press). If you have multiple people if they stay right behind the player holding the shield they will be safe, but be careful as usually there will be a some horizontal motion of the shield-holder due to knockback. If you fail to shield yourself from this attack it pretty much mean death, though the damage is not truly instant so if you are only out of the shield for a short time, you may survive. Shortly after this breath attack drop the shield and the dragon will quickly start to chase you again. You can leave the shield, as at the next stopping point there will be another crate with another shield inside. You get a total of four times where you can fight the dragon this way, after the fourth time the dragon will chase you out an exit and onto a cliff. Continue to run along this cliff (the dragon can still hurt you as he is chasing you at this point), and eventually you will reach a dead end, at which point the ledge will collapse dropping the dragon into the chasm and you will get the C ending to the level.