Can someone please tell me how to get in the sword room? I'm starting to feel retarded.

GOT IT! If you have all your Red hearts full, the door will be open.

Beating the boss should open it.

Beating the boss doesn't work, I tried that, went back after beating him and it was still closed

I've been wondering the same thing. It seems kind of random.

I'm not entirely sure on this but in my experience if you take any hits while clearing out the room the sword door is in it refuses to open. Maybe the key is not taking any damage?

You have to have full health, if you heal up and come back it will be open.
 
This is the only way to open it and I've confirmed it myself several times.

Don't cross swords kids.

you don't need full health. It seems like you need at least 4 or maybe 5 hearts. Blue hearts count.

@D_W said:

you don't need full health. It seems like you need at least 4 or maybe 5 hearts. Blue hearts count.

Oh, I didn't realise you could get in with 4, I thought it was a minimum of 6 - perhaps it depends on the character you're playing?

@BeachThunder said:

@D_W said:

you don't need full health. It seems like you need at least 4 or maybe 5 hearts. Blue hearts count.

Oh, I didn't realise you could get in with 4, I thought it was a minimum of 6 - perhaps it depends on the character you're playing?

The number doesn't matter, it's just full health. I've had them open when all I had was 3 red hearts, but never when I didn't have full health. I have heard the blue hearts count towards it. So, if you have 3/4 of your normal hearts and 1 blue heart, then the door will still open.

It might be random when you enter the room as well. I've had it where I left the room on accident and came back in and it was locked.. I walked around for a bit in other rooms then came back and it was open again. I don't quite remember if I took any damage, what my health was etc.

@BeachThunder said:

@D_W said:

you don't need full health. It seems like you need at least 4 or maybe 5 hearts. Blue hearts count.

Oh, I didn't realise you could get in with 4, I thought it was a minimum of 6 - perhaps it depends on the character you're playing?

The number doesn't matter, it's just full health. I've had them open when all I had was 3 red hearts, but never when I didn't have full health. I have heard the blue hearts count towards it. So, if you have 3/4 of your normal hearts and 1 blue heart, then the door will still open.