I would think that the Lord Ruler holding the power caused the Ashmounts. What caused the Deepness, however, is a different question entirely. I believe it is a thing brought up by Ruin's existence, so, whenever Ruin has the ability to influence the world, the Deepness logically follows.
There is another matter here, though. It is the "Hero of Ages". Brandon said on the annotation for the title page on MB2:
This title was fairly easy to choose. Actually, the titles of all three books were easy to choose. I originally toyed with calling the Hero of Ages the Final Hero. So, because of that, I was tempted to come up with a "final" title to use for book two.
However, I quickly decided that I liked Hero of Ages instead of Final Hero (you'll see why in Book Three.) So, way back as far as the first chapters of book one, I was planning book two to be named the Well of Ascension.
"Ages". As in, multiple ages. We can assume what an "Age" is is the thousand-year span between Ascensions. As to why it is called the Hero of Ages, we can only speculate.
So... we better start speculating on that, stat. It's what we do around here.
Andrew, you're welcome. That political crap is really draining, considering I have a lot of homework to do.