The Heretic (Main Quest)
This quest auto-populates at the end of Aten Rising. To start, you'll need to take out local crime magnate Tychon, who moves back and forth between the Temple of Hatshepsut and the nearby wharf.
In many ways, the Temple is the easier killing ground- lots of guards, but also lots of walls and visual obstructions. As usual, approach from the southern pyramid to reach the causeway terminus undetected.
The wharf is much smaller, but between the local soldiers and Tychon's own guards, it can get a little crowded.
Still, you've got your arrows, and the patches of tall grass can give a surprising amount of cover. When Tychon is dead, take the ledger from his body.
The statue in question is inside the treasury of Hatshepsut's Temple. If you've already looted the temple, you may remember this as the secret room with one of the location treasures. This time, the window in is helpfully marked for you.
Examine the large statue of Amun to get your next objective.
The Tomb of Akhenaten is even more straightforward than Nefertiti's- just walk forward, past the sarcophagus, and into the glowy light.
As ever, the walkway to the hereafter is guarded by Anubis soldiers, but they can be sniped without penalty.
Past the guardians, dive into the water, and swim through to emerge in the realm of Aten.
No purification rituals here- your goal is smash the five relic statues scattered about the realm. One is very near to your starting location here.
The other four statues are instantly populated on your map, so no guesswork there, just find and smash (though it is recommended you loot the Crocodile Lair to the north before leaving the starting area- it has a box of 20 star shards just sitting there). Note also that the relics can be smashed by projectile weapons, but it will take mutiple hits, and the statues do not show incremental damage.
For more info on those locations, check out our guides for the Wharf of the Aten, Royal Palace, Vault of the Aten, and The Chambers of Reflection. Once you've smashed all statues, the sun itself will mark the point of Akhenaton's return.
Approach his throne to summon the man himself. Or his corporeal wraith, or what-have-you.
The heretic's sword is slow, but very powerful, and cannot be interrupted by damage. A reliable tactic is to slash and dodge around him- not performing combos, but just one or two stabs per attack before dashing under his blade again.
Bows do next to no damage, but they can be used to break his attack pattern, giving you an opening for damaging strikes or heavy weapon hits.
Also, despite his size, you can still throw him around with overpower attacks, like the spear's.
His destruction completes the mission, and gives you his sword, The Living One. The main quest continues with Isidora back in Thebes, and the end of the Gods or Creed sidequest is now available.