Question:
Beyond the corners of the mind, lies the power of the Earth, the source of salvation, and the coming of evil

Answer:
PSI or psychokinetic energy

Explanation:
Beyond the corners of the mind, - PSI is beyond the internment of our mind. It is generated there, and is unleashed beyond it.

lies the power of the Earth, - All your sanctuary locations around the earth magnify your power. In a sense, the power of the earth is energizing you.

the source of salvation, - In the end, it was Paula's psychic prayers that defeated Giygas, and restored peace to the world.

and the coming of evil - Giygas influenced the minds of other people, animals, and monsters. It was the beginning. The beginning of a war, bound for Earth.

YEAH!!! You two rock! And everyone else, you all had great guesses! Now this is amazing. 2 out of more than 100 people got it right! Though, heh, that really isn't that strange in the world of HARD Trivia (hee hee, I live in my own little world!). Well, it's time for me to go to bed, and time for YOU to blow-up some brains! Oh, and speaking of brains, last Thursday, I went in for an MRI. I got to see whats inside my head! And I was right! Hamsters! Gwahahahaha! NOW GO PLAY OR PLOQAZ WILL EAT YOU!!!!!