I'm not sure on that number either kelwl
I'm still waiting to get enough bronze wyverns for a gold dragon, though my fifth tower should come soon. However note that the cult you need 380 k mana and you need to upgrade your mana storage capacity as well as the speed, so I've been hitting those buttons along with the other upgrade buttons.
I hope the cult isn't just a way of ending the game for everything to happen again since that would be dreadful, and if so I'll be giving a zero star review on the ap store, though as it is I can't say I'm too impressed albeit I think I might as well see the dam thing through to the end since it's not exactly mind taxing to go hitting those rotten upgrade buttons :d.
Our souls with high music ringing; O men! It must ever be
That we dwell in our dreaming and singing, A little apart from ye. (Arthur O'Shaughnessy 1873.)