Blasphemous – Requiem Aeternal: How does it work?

Introduction

I’ve noticed that theres A LOT of people asking about this for some time now, and the stipulations for getting it are not widely known or even properly figured and collected into a single post, so I decided to do this for everyone else who wants to attempt this. 
 
Although the achivement says “beat all bosses without using flasks,” there’s more going on under the hood that you’d initially be led to believe. So, after having 150% the game 7 times, 5 of those in a row and with all penitences, and gone through the Sacred Sorrows, as well as doing some investigative work on Google, this guide contains what I figured based on all the information I’ve got 
 
 
 

Why can’t I get the achievement? Explain!

In short, the achievement is outright misleading. These are the REAL things you have to consider the moment you pursue this achievement: 
 

The requirement is to not use flasks in boss areas, not just in boss battles.

The game has designated boss areas that follow the following format: 
 

<| save room | boss room | quest item | deogracias (or npc) |>

 
So if you use your flasks in any area like this, you’re void of the achievement. There’s a few exceptions to the rule (such as Crisanta and Escribar) but generally speaking this is how the areas are structured. Confirmation of flask usage reset by allowing the boss to kill you on PC is needed, currently only works on console versions 
 

You can get the achievement ONLY on a fresh save file, not an ascended one.

This one is what most likely made everybody feel like the achievement is bugged or something, but the reality is that your flask usage carries over through your ascencions, meaning that the very first time you play a save, you gotta get the achievement. AFAIK, this is not the case for the console versions, due to how achievements work in those systems (they have a separate counter that works similarly to that of the game, but doesnt carry over across ascencions so you’ll always have another shot at it) 
 

You only have to beat the original 9 bosses.

10 if we count phase two of the final boss. The Amanecidas work in a different way than the others, but you can also do them for an increased challenge. Mini-bosses such as Perpetva or the Wardens at Holy Prohibitions don’t count for the achievement, but if you want to be safe you can go without flasks at them 
 

You cannot get the achievement in Sacred Sorrows.

This is kind of obvious, because for the keen eyed, the bosses all have had their health values nerfed and become slightly more aggressive, meaning that you don’t need a lot to power through them, especially considering that this mode is only unlocked after completing the game at least once and you’ll probably have all the tools at your disposal to cheese the bosses 
 

You can accept Viridiana’s help.

So long as you don’t use a flask, you can get help from her. The wind up before her recovery triggers makes it a balanced deal 
 

DO NOT use the Heart of the Holy Purge.

It disables you from using flasks and gets you a bit of health on kill, but for some reason it also voids the achievement as well 
 
 
 

Last words

This guide will be updated as soon as possible, for the designs of the Miracle are capricious. If you have more information that pertains to the PC version specifically please let me know, as this is my penitence. 
 
Sorrowful be the heart, Penitent One. 
 

Hope you enjoy the Guide about Blasphemous – Requiem Aeternal: How does it work?, if you think we should add extra information or forget something, please let us know via comment below, and we will do our best to fix or update as soon as possible!