I might as well do a boss guide for anyone struggling with the game on normal and doesn't mind spoilers.
1. Convent boss fight
The easiest one, since it teaches players to go for boss weakpoints for the +50% damage bonus. Hit the parasites from a distance with accurate arrow shots and it'll go down fairly quickly.
2. Pregnant villager's monster foetus
Although not repeatable first time round, the fight is the same once players lose the infertility blessing and have to treat their own pregnancies in the same manner.
Boss flies around in a horizontal wave pattern and drops enemies (leeches) when struck which will QTE grapple the player to a loss (and the game-over cut-scene removes the infertility blessing). Infinite leeches will also drop from the sky as the battle progresses. The fight itself shouldn't be too difficult, have potions on hand and hit the boss when it flies low enough for the standard magic sword's upward swing to make contact. Hit the boss enough to expose its core and a few jumping strikes with the magic sword will bring it down.
3. Oversized leech in swamp.
The weak spot is the face on the leech, stand reasonable close and the upwards aimed shot (hold up before using the magic attack) will hit it fairly reliably. The attack repertoire given below:
1. Rain of leeches: Move aside from the telegraphed drops, and if any big leeches emerge from the ground simply kill them for MP recharge.
2. Submerge and charge: If it hits you that's a lot of HP damage and a knockback against the house wall forcing a QTE to recover. The magic sword attack timed correctly will stop it completely.
3. Multiple big tentacle attacks: If one appears directly behind the player, jump to evade it.
4. Triple leechball spit: Evade or use the magic sword attack to take them out.
4. Monster den boss
The hands with the jewel are weak spots, and they are wide open after they whiff an attack. Once players figure out the attack pattern and have a handle on the support fire, this boss falls easily.
1. Hand smash: Raises hand twice before slamming down. Move out of the way or keep jumping just as it goes for the attack to avoid it completely.
2. Hand grabs: The left and right hands will take up positions to do grabs. Stay in the centre and either jump or dodge as the series of three is executed.
3. Goblin summons: Infinite respawns, so don't bother with them and just avoid or hit the spears out before they hit you.
5. Gravekeeper
Infinite summons of zombies, so fight through the waves and jump up to where it is and just attack it until it teleports away. Quest from the lady in the hut before the east exit of the town must be taken before it will spawn.
6. Pigman farmer
Infinite summons of parasite pigs from the left, while the boss slowly closes distance and hits the player for high damage with its weapon. Take out the pigs as they come, avoid their death-release parasites and concentrate attacks on the boss until it falls.
7. Town raid - Goblin chief
Players have fought the spear-armed goblins before in their lairs. Hit it from a distance with the arrows to get rid of the mask and then hit it some more to kill it.
8. Town raid - Goblin war wagon
The goblin with the shield up front must be killed before players can hit the ones behind. Watch out for the wagon ram, which has the same knockback as the leech boss with even more damage. Once players get rid of the shield and can board the wagon, it shouldn't be difficult finishing off the remaining goblins.
9. Parasite priest (do this first instead of finding the underground canal route to the castle)
Can't win the first phase when it materialises in front of the locked door. So let it attack and drain HP to zero.
10. Parasite priest rematch
Read DarkFire's post a few above mine for details. In summary, this quest sequence has to be done more or less in one go to stop it from breaking and resetting progress. Bring enough potions of all types as this is a long stretch and even the grunt enemies hit hard. Once players get to the statue and learn the AOE arrow skill, that's the rest spot before the boss.
The shield the priest relied on for the first phase can now be broken with the AOE arrow attack,. so charge it up and hit the priest to drop its shield. When it teleports above the player, watch where the tentacles are thrown and destroy them for MP recharge. Rinse and repeat.
11. Parasite brain gestalt
The priest's second form. It will drop infinite numbers of spawns which will grapple the player and win through attrition if players don't fix the corruption with white potions. Simply aim at the "brain segments" and hit them until they are destroyed. Each destroyed segment will then periodically throw out tentacles to weaken the player. Either use the piercing arrows or the AOE attack to hit as many segments as possible, and once players can't reach the segments from the ground climb the platforms (watch out for tentacles) and shoot down the last segment and the boss core to finish the fight.
12. Beast stomach
Found at the end of the "traverse the monster innards" dungeon, it's a run and gun boss fight where players have to keep distance and shoot the head with jumping arrow shots (no need to aim as a stock jump from distance with an immediate arrow shot has a decent chance of hitting the weakspot) while avoiding the antibody cells and taking care not to get caught by the ambushing monsters in slime pools. The boss will periodically stretch out its tongue to grab the player and draw her in for consumption, so button mash to escape and use White potions to clear corruption to ensure the QTE will succeed. If players keep to the right edge of the screen when the tongue is unleashed it won't have the reach to catch the player.
13. Eye pillar castle mid-boss.
Found 2/3rds of the way through the palace dungeon. There's a row of hooded priests and the eye pillar at the end of the room constantly shooting beams at the player. Players who have the float jump skill will find it easier to avoid the bottom eye's beam attack. Simply get close and strike the eyes when they're open before they unleash their painful attacks. After doing enough damage, the priest closest to the pillar will do some kind of staff attack which knocks the player back to the left edge of the room for minor damage and a QTE check to get off the floor. After that attack, the beams will change trajectory slightly and will fire more often. Still the same strategy of getting close (or close enough to use the AOE arrow attack) and hitting the eyes while they're open. Another priest attack will trigger after the boss's HP drops below another threshold, but it doesn't change the pattern. Avoid the beams and hit the eyes while they're open and it'll eventually fall.
14. Eye monster in front of castle entrance
Players can take this on by destroying the flesh wall once the piercing arrows magic skill is learnt. The boss itself gives little room for error when it's tackled early due to high damage, but it's beatable once players learn the pattern. Aim for the eye with arrows or just hit it at close range with the magic sword. The attack pattern is to summon three stalagmite tentacles from the ground to impale the player, while the eye throws out eldritch young to drain the player's HP and MP with QTE grapples. Stay alert for the tentacle impalement and kill the spawns as they come while keeping up damage on the eye. Occasionally a spawn with blue eyes will show up, that's the MP recharge mechanic for this boss (the spawn even turns away from the player when active).
15. Palace - Kitchens (Possessed Boar)
The living vine enemies are a nuisance, so use magic arrows or the magic sword to get them to retract enough to move through them. Piercing arrows are a must for this segment.
The oversized pig is like the pigman before him: Use arrows to hit the head and mouth weakspots (cluster of eyes) when they're exposed to get the damage in. It closes the distance and once it's in grab range players will likely lose as the eat pounce will eventually wear players down, so aim the shots or use the AOE attacks properly to finish it off before it can close the distance.
16. Palace - Library (Snail gestalt)
Heed the warning in the save area about not directly meeting the gaze of the snail (instant death if it drains HP to zero, base damage 50).
The snail gestalt initially starts with four circular "anchors" which hold it in place in the roof. They will shoot beams at the player which can be attacked and struck down for MP recharge. Players have to destroy the anchors with aimed arrow shots. The snail itself will use a powerful beam attack which instantly kills players if they look at it, so keep the player's back to the snail when it charges up and avoid attacks as best as possible until after it fires. The second phase is just one anchor, but it's close and fires beams really often, so players need to find a position to spam arrows quickly enough to take it down before they are killed in turn.
17. Palace - Treasury mid boss (golden hands)
Four arms (two on each side) will appear and try to grab the player for a QTE struggle. If players fail it, they are turned into golden statues. Simply attack the arms and wriggle free from the QTEs as fast as possible to win.
18. Palace - Treasury painting boss
The painting will reveal its weakpoint (exposed eye) when it spawns, so players can use regular attacks or magic sword attacks to attack when the opportunity presents itself. When the eye is closed, the painting will close the distance with the player in an attempt to force a QTE (which if failed is a game over). Use regular attacks and magic swords to push the painting back in its relentless charge until the eye reappears. Rinse and repeat. Having a white potion for this fight makes it far less dangerous.
19. Final boss
As instructed, use the quest item when the player and the NPC reach the top. The shield will change colour (red is the last level) as more boss spawns impact it, so players have to defend the NPC for a set amount of time for victory. The boss will periodically use a super laser beam attack which tracks the player briefly before firing, so move away from the NPC shield when it appears and move away when the beam stops. MP shouldn't be a problem since the spawns sometimes drop MP recharges on death, players have to watch out for the tentacle spawns which home on the player's location and deal significant HP damage from impact and the residual cloud. Towards the end, the spawns will get vicious in their quantities so players need to hold one end with the magic sword and use the AOE arrows for the other.
For the final QTE at the cutscene, it should be doable with even minimal corruption although it is time limited. Once that's overcome, the game credits will roll.
20. Hidden boss (invisible lizard)
Found at the area with the two pillars just before the goblin cave, players use the same item which makes the final boss visible to trigger the fight. Method to beat it is given above this post. Players just need to destroy the laser orbs when they spawn nearby while hugging the pillar closest to the boss's location and hitting it with magic sword attacks. When it switches pillars, the strategy doesn't change. For the multiple laser sequence where 5 of them spawn and fire in consecutive bursts, players can outrun the sequence with a running jump towards the end after positioning for the first wave. Worth fighting this one, as it drops the best weapon in the game as a reward.
