A demon door in barrow fields says I can only enter when I have a lot of..

For the demon door saying you need to do something evil in front of it, kill someone in front of it, or eat several of that Crunchy chicken food.
For the demon door in barrow fields, I think you have to become fat to open it.

First in barrow feilds, EAT TILL YOU GET FAT! Eat a lot of red meats, pies and drink beers quick till you get fat( you can check how fat you are in the start menu, in personality)then talk to the demon door, it sould open.
And for the other one. You have to kill like 4 people in front of it( traders, make them follow you then kill them in front of the 'awake' demon door), or eat at least 10 crunchy chicks, or be fully evil.

Hope this helped
Dark-Dragon-Master

To get inside the door at barrow fields you need to eat alot of meat and get pretty fat.

And for the other one you need to eat 10 chickens in front of him and you should be able to get in

Demon Door #2 (Greatwood Gorge)

This door requires you to exhibit a display of "evil", and shouldn't pose much of a problem unless you're planning on staying strictly "good" through the game. To pass through, you must murder several commoners in front of it (traders, henchmen, etc), eat ten Crunchy Chicks, or already have horns and billowing red smoke. The reward for your vile efforts is a Legendary weapon - Wellow's Pickhammer. Hope this is a big help, it sure helped me

For the demon door that says"u must do somting of great evil in my sight" you have to become evil and then it says "master, your great evil surround you like a shroud! Enter." and then you go 2 the island in the middle of the place and you get willows pickhammer! (legendary weapon!)

Hope this helps u!

I was only able to open the demon door asking for a great evil after becoming as evil as possible.

The demon door in Barrow Fields just wants you to get fat and talk to it again. You can lose the weight again easily enough by running and fighting.