For 2 years I have obsessed over this particular code and even though I can produce it at will I cannot figure it out. I'm hoping that someone with a brain far larger than mine could take a crack at it and end my misery. There is an online resouce where you can encode plain text into this code and that website is:
http://www.mutford.net/geocache/tenebruscode....

The cipher text is:

6826183516 0699262046 4372343765 2460232274 4484941597
8024045693 7318345669 9513557420 6064311529 8631542182
0559315441 5841469130 4817877616 4464599286 8458654491
7208597444 2877814789 5125679030 3544010085 8746695404
6260811415 7347264090 1034440264 5165954826 0808482982
0139016936 7086875449 9735175635 6669040156 982237848

Please help if you can!