Blasphemous

Fairly straightforward. You have to beat all named bosses (the ones with health bars) without consuming a flask. Do not use a flask until you are out of the boss room. The game expects you to beat the boss and leave the room without using a flask (needs confirmation). I do not know if Perpetua counts as a boss for this achievement, I read on a youtube comment that she doesn't but I recommend killing her without using a flask anyways, just in case.

You are allowed to use Viridiana for this. Use her on the following boss fights (you can't use her for the last boss fight):

Tres Anguistas - very annoying because the spears are hard to dodge.

Exposito - his erratic movement makes this harder than the others.

Out Lady of the Charred Visage - bullets can be hard to dodge

The other bosses aren't that difficult in my opinion and the last few bosses can be killed after you get tons of upgrades. Make sure to use the right defensive rosary beads for the bosses. For example, Cristana does heavy magic damage. Equip all magic defense items and the frozen olive and you become a walking tank against her.

While it is not too difficult when you're an experienced player on your first playthrough, I would recommend doing this on NG+ simply because after unlocking all of the Rosery slots you can equip the right gear to make yourself invincible and save yourself from getting stressed (and raise your defenses significantly on the way to unlocking them all).

You can use Viridiana during boss fights to assist with the first few bosses if you really struggle (which will lead to the Dying Breath achievement) as it's free healing during the fights.

You will need to ensure that you have at least gotten the achievement for all Rosary Beads, and to avoid risking using a flask accidentally, have the Heart of the Holy Purge equipped.

Beads to equip;

• Frozen Olive

• Light of the Lady of the Lamp

• Consecrated Amethyst

• Ember of the Holy Cremation

• Token of Appreciation

• Quirce's Scorched Bead

• Wicker Knot

• Silver Grape

You will be safe to lose 90% of your health and proceed to take 0 damage from enemies and bosses. Consume all of your flasks to deal extra damage, equip the Heart of the Holy Purge if you don't want to risk accidentally using one, or if you trust yourself, equip the Heart of Saltpeter Blood to increase your attack further once you reach that 10% health remaining mark.

As no one has stated this in other guides. This can be done in ng+/true torment mode and I would recommend doing it this way. Your prayers, rosary beads, Mea Culpa hearts and relics all go to ng+ and makes some of the bosses trivial. However, you will have to find health, magic, and rosary knots again in ng+

The only issue is that you take more damage and deal less overall. This isn't as noticeable in the bosses as it is in the open world. It makes getting around a chore due to some enemies dealing a lot but not taking much. But donating 20k to the church in Alberto does help with the checkpoint traveling ,so make sure to do that first.

I also equipped the Heart of Holy Purge Mea Culpa Heart before each boss. This heart removes the flasks entirely so no worrying about hitting the button accidently. Also guilt pick ups are very helpful for healing ,getting magic back, and this does not void the achievement. Its almost worth going in there and dying just to have one in the arena. Finally the frozen grape bead is essential as it stretches the last 10% of your health so much, I lived a lot longer then I thought I would with this equipped

Here are some tips that I found helpful in the bosses:
Warden of the Silent Sorrow - This should be a quick fight with any prayer/combos you can pull off just watch out his attacks can one shot you now

Ten Piedad - slide thrusting, aerial combos combined with prayers and you can get him down fast

Tres Angustias - Viridiana is pretty essential to this fight so I would recommend using her here - Zarabanda of the Safe Haven prayer really comes in clutch as sometimes you can get to them but not land good hits and this will ensure all of them take some hits. I did a lot of slides and ground combos where I could. I would also recommend making trying to get an extra health upgrade, I think i got the one at the bottom of the desecrated cistern with the relic that lets you survive the falls

Our Lady of the Charred Visage - Zarabanda of the Safe Haven prayer will block projectiles and hit her with your jumps

Esdras -you have to learn the move set and block/parry alot get the lightning rosary beads to take less of the damage attacks. When his sister shows up be aggressive and end the fight fast, do not worry about her

Exposito -Debla of the Light prayer absolutely destroys this boss i think i had to do it 4 times and he was dead, just make sure not to get grabbed

Melquiades - make sure to kill the edge hands first and he likes to go off screen. I used Zarabanda to hit everything consitently, also the ranged attack is very helpful

Quirce -you have to learn the move set and block/parry, slide thrusting is your friend.

Crisanta- I saw in another guide say make sure you have all magic/status/defense beads on at this point and it helps alot. make sure you have all the upgrades and it shouldn't be too bad. Alot of parrying and you should be good. she has a move that she parries you but you can parry right back and then punish, used that a lot.

Escribar (Phase 1 of the final boss)- I would put the Thorned Symbol bead on as his touch damage is kinda bugged in this phase and you will get hit when he is invisible. I found having Tiento to your Thorned Hairs prayer on and when he does his fire ball attack using it then doing the 4 piece combo over and over on him once the shield goes down is really effective, only had to do it twice and the fight was over.

Last son of the Miracle (Phase 2 of the final boss) - Seemed intimidating till I switched to Debla of the lights prayer, once he opens up use the prayer 4-5 times and he should be within a few hits. once he gets to his last bar be aggressive and you should have it.

This achievement requires you to kill all 11 bosses without using bile flasks. You can have Viridiana assist you on 3 of the 5. Achievement progression will increase for each of the bosses successfully killed without flasks. After every boss, get in the habit of seeing that the counter is accurate or else dashboard and try again. The achievement requires the following bosses:

Warden of the Silent Sorrow
Ten Piedad
Tres Angustias
Our Lady of the Charred Visage
Esdras

Exposito
Melquiades
Quirce

Crisanta
Escribar (Phase 1 of the final boss)
Last son of the Miracle (Phase 2 of the final boss)

The final boss is counted as 2 unique bosses which I think is the source of confusion for the counter. Perpetva has a single attempt boss fight that does not count ( if you die, you can’t even fight her again, she simply despawns when you return).

Specific boss strategies are to taste and most players will probably find their own way of dealing with them but I personally found good blocking a mandatory skill for Esdras, Crisanta and Quirce especially. Collecting health, magic oil and Mea Culpa upgrades are a must. The Gemino quest also gives the Frozen olive rosary charm which I find extremely helpful.

For Viridiana, you can use her for 3 of the 5 being;
Ten Piedad
Tres Angustias
Our Lady of the Charred Visage
Exposito
Melquiades
I would recommend her for Tres Angustias, Our Lady and whichever you struggle with more between Exposito and Melquiades. I find once you get an easy positioning on Exposito and can hit both of his weak points, he’s not so bad. Melquiades is a longer fight and I used her here as I got sloppy near the end and tended to like to just tank through his magic and summoned hand attacks. Your choice.

Good Luck! I recommend learning the game through one playthrough first before attempting this. Learning the bosses and the world’s tools helps a lot.