Era of Man
The Ten remained the dominate religion of Haven, and eventually several parts of Solith, for nearly 400 years. The success of the Ten is mainly attributed to the lack of truly organized faith within Haven until the pantheon's growth. With organization came proper funding to educate the masses of the Ten and build places of worship for each Exarch. Though each Exarch was in agreement that maintaining their pantheon was beneficial to all parties, the sheer diversity of each Exarch and their domains led to constant infighting. This power struggle would lead to the eventual death of Lady Death and the uprise of a child-faith, the The Nine.
Note to Self:
Figure out the exact dates the first 10 were worshipped as a functioning Pantheon. It ends at the 1st of Fall, likely. As soon as Lady Death is no longer part of the Pantheon.
10 > -Lady Death > 9 > +Lady Death - Elias - Ram > 8
Era of Man - Era of Fall - Era of Rebirth
The reign of the Ten would collapse in the 1st of Fall, as soon as word of Lady Death's death was made public. A new pantheon would rise from the ashes as The Nine. When Lady Death's was brought back from the brink, both Ram and Elias were lost. This would lead to the creation of the current pantheon, The Eight.