Warning: This guide contains spoilers!
How To Reach The Ending
There are two endings in Demon’s Souls and which one you get is based on certain decisions you make at the end of the game - these endings will not be based on the accumulated choices you have decided while playing the game. Once you’ve cleared all the areas and defeated all the bosses and the False King Allant, you must go to the bottom of the Nexus to meet the main antagonist of the game by interacting with the Maiden in Black. After you defeat the Final Boss, you must head further inside and reach the final destination and make your final decision.
Other Things To Remember
You cannot level after you’ve cleared False King Allant in 1-4. In order not to trigger the last section of the game from appearing, you must not defeat False King Allant since this prevents you from talking with Maiden in Black to level up. Fortunately, you can carry over your accumulated souls into NG+. Still, the Final Boss is surprisingly weak as compared to what you have faced the entire game. It is not even the case that you need to have mastered the game at this point, to be able to say that the Final Boss is easy, he is just a plain cakewalk. You really do not need to level up further if you managed to reach this part of the game. There is no need to be afraid if you happened to trigger the final section of the game.
Demon’s Souls Bad Ending
For the “bad ending”, you must kill the Maiden in Black. This allows you to take King Allant’s place and permits the Old One to cover the whole world in Fog. You will earn the Beast Demon Soul and Red Eye Stone for choosing the Bad Ending for your next playthrough in NG+. These rewards are very useful, but we recommend to choose the “good ending” instead because its reward is better even if it is only one item. Then you can choose the “bad ending” in completing your NG+.
Demon’s Souls Good Ending
For the “good” ending, you just let the Maiden in Black do her job in lulling the Old One to sleep. Both she and the Old One will vanish as you did not let temptations cause you to choose the destruction of the world, instead of saving it. You will gain the Maiden in Black Demon Soul. You can exchange the Maiden in Black Demon Soul with Yuria for a Soulsucker. The Soulsucker is magic that can drain the enemy’s souls. This would allow you to gain more souls than you would get when not using the magic, and it kills enemies in one-shot, of course, with the exception of bosses and greater enemies.