Clicker Heroes last extension includes Cadu and Ceus Tomb Guardians. Unlike the other heroes which are used one at a time as the player advances, Cadu and Ceus are available as the player reaches zone 285K where the gold earned is enough to hire them both.
After getting past Xavira, both Cadu and Ceus are available at the same time. Even more peculiar is that the hero upgrades affect each other. It does take several ascends to reach this point but the Maw awaits with an even higher cost to activate. The final few heroes cost a staggering amount more than the lower ones.
The upgrades for Cadu and Ceus alternate in cost and benefits. The upgrades are alternate in cost and Cadu/Ceus have upgrades for each other in alternate as they are reached. The upgrades are all different in cost so they are activated one at a time.
The upgrades are staggered so leveling each one together is slower going than the earlier heroes up to this point. One thing to keep in mind is that the grinding ahead is outright brutal. The last achievement is for zone 1 million which is far from where this screenshot shows the player to be be.
Deeper into the game it can be seen that the Maw is also a brutal hill to climb. The Yachiyl is where I was before I needed to ascend to get more hero souls. The cost of the first Ace Scout is 4.45e107995 which far above zone 885K. Auto clickers are definitely handy. All the rubies earned as spent on rubies and clickers can help push to higher zones which is the only way to reach the last hero and the game is beat,