Cuphead

"Survive the nightmare" means that you have to fix the Broken relic into the Curse relic via the secret boss. But this achievement is only a part of another achievement (see more below).

Here are all the steps you need to complete for this achievement.

• Buy and equip the Broken relic for 1 coin in the shop
• Solve the Graveyard puzzle to unlock the secret boss
• Beat the secret boss so that the Broken relic becomes the Cursed relic

Now a little detailed information about the individual steps

Graveyard puzzle

The solution to the puzzle is in the three statements of the three people on the winner's podium. There hide the directions in the messages. The order is first place, second and then third place. Unfortunately, these hints are different for everyone! In the spoiler you find many solutions which I gather together.

With your personal solution, now go to the graveyard and open the path to the secret boss.

Secret Boss

I personally stood all the time in the lower left corner and shot with the new red shot, the angel boss who then forwarded the shot to the devil boss. In between, of course, dodge the shots and co. Should not be too difficult I think.

After you beating the boss you obtain the achievement but that was not the end. You can still turn the Cursed relic into the Divine relic aka Paladin achievement. The next part is required for the Paladin achievement (Obtain great power)

Defeat 7 bosses with equiped Cursed Relic

This is definitely the hardest part. You must defeat the bosses at least on regular difficulty. The problem is, with the Cursed relic you only have one HP and every time you press the firebutton or dash, a different shot comes out. That makes things really hard. All bosses on all isles count (for me)

Fortunately, there are also a two major tips:
- With every 3rd parry you get a HP in addition
- There is also an official cheat from the developers that also gives you an additional HP. To activate it, you have to turn in a circle / spin around on the map very quickly. Once you have finished the game (main or DLC), you can use the cheat on each island infinite but if you have neither the main game nor the DLC completed, you have only 3 wishes! on the specific isles. So be careful where you use the cheat. Once activated, the cheat remains active until you have defeated a boss.

With these 2 tips you have basically 3 HP, which makes the whole thing much easier. But it is still challenging!
You can see your boss progress by the Cursed relic, it changes appearance every two defeated bosses. After the 7th boss you will obtain the Paladin achievement and the Divine Relic. Congratulations!

Video Guide

This achievement is linked to the secret boss that you access via the graveyard puzzle.

To unlock the boss you need to find the 3x3 grid of gravestones and interact with 3 of them in a particular order. The order is random for everyone. The key to solving the puzzle is in the dialogue you have with the climbers on the podium.

Start by talking to 1st place and look for a directional keyword such as "left/right/up/down", then repeat with 2nd place and 3rd place. For instance, my dialogue with 1st place was "I'm the winner and all is right with the world." "right" being the direction.

What this gives you is a set of directions.

Head back to the graveyard and use the middle gravestone as the starting point. From middle gravestone interact with the gravestone in the direction you read from the 1st place dialogue. A blue ghost will appear (whether it's the right order or not). Then move back to the middle. Rinse and repeat with the 2nd place dialogue, and finally the 3rd, moving back to the middle each time.

If done in the right order, the middle gravestone will light up blue and you will be able to interact with it and battle the secret boss. Once you beat the boss you will unlock the achievement.

Here’s a video guide by provided by Maka91 (cheers Maka)