Dark Aeon

The Dark Aeons are antagonistic counterparts of aeons in Final Fantasy X. They are superbosses and one of the extra features included in the International, PAL, and HD Remaster versions of Final Fantasy X. Each has a red spot somewhere on their body and appear as darker-colored palette swaps of the aeons Yuna can summon. Though the possessed aeons during the final battles use the same models, they are not referred to as "Dark Aeons".
In the Japanese versions the enemies' names are prefixed with "Heretic" , but the collective is still referred to as "Dark Aeons" in Japanese publications.
==List of Dark Aeons==
Once Yuna and her guardians escape Bevelle, Dark Aeons appear to halt their journey, some blocking access to previously friendly locations, while others wander in inconspicuous locations hoping the party would come across their path. Returning to some of the previous locations is made impossible until the player defeats the Dark Aeon, which can make things tricky if the player did not obtain all items in these places yet, such as the hidden treasures in the Cloisters of Trials, the Sun Crest in Zanarkand Dome, or the second Overdrive for Valefor and the Jecht Sphere for Auron's Bushido in Besaid Village.
Each Dark Aeon boasts very high HP, with Dark Anima topping the scale with eight million. They have supreme stats and are immune to status ailments. They drop weapons and armor with Break Damage Limit and Break HP Limit, along with other high-level auto-abilities, such as Ribbon. Some of the Dark Aeons' abilities are non-elemental, such as Dark Shiva's Diamond Dust and Dark Ixion's Thundaja. Thus, Elemental-Eater abilities have no effect.
Though the player can't usually summon their own aeon against another copy of itself summoned by another summoner, the player can summon aeons against their Dark Aeon counterparts.
===Dark Valefor===
Dark Valefor is available after escaping Bevelle and after the scene of Tidus and Yuna's waterborne date. If the player is going to challenge it before acquiring the airship, the player must walk all the way back to Besaid via Thunder Plains, cross the Moonflow on a shoopuf and take the ferry from Luca to Kilika and on to Besaid. At the entrance to Besaid Village, a summoner blocks the party's entry and summons Dark Valefor, who must be defeated to return to the village.
The pre- and post-battle cutscenes use recycled dialogue from early parts of the game. If Valefor's second Overdrive, Energy Blast, was not obtained before the Dark Aeons spawn, the player will have to defeat Dark Valefor to obtain it. One of the Jecht Spheres Auron needs for his Bushido is located in Besaid Village. Unless the player makes a long trek back to Besaid after Jecht Spheres are unlocked, defeating Dark Valefor is the only way for Auron to learn all of his Overdrives.
If the player does not open the chest in Besaid Temple, defeating Dark Valefor is required to get Anima.
===Dark Ifrit===
After obtaining the airship, Dark Ifrit is found at the entrance to the now-inaccessible Home on Bikanel. If the player approaches the former entrance, a summoner disguised as an Al Bhed woman will ask for their assistance, luring them into a trap where Dark Ifrit pounces if they try to peer over the edge of the canyon. The appearance of Dark Ifrit relates to the Home glitch that affects some International versions.
===Dark Ixion===
Dark Ixion is available after viewing the arrival cutscene of Calm Lands. The first battle against Dark Ixion will initiate after talking to the Warrior Monk in the northern area of the Thunder Plains. Dark Ixion must be defeated twice before he will disappear and the player can escape the battle. The second battle with Dark Ixion can be avoided until the player is ready, allowing for items to be restocked. Dark Ixion uses different attacks between the first and second battle.
===Dark Shiva===
Dark Shiva blocks the entrance to Macalania Temple and is summoned by a group of Guado. Once she is defeated, the Guado will chase the party away from the temple, like they did after the defeat of Seymour Guado. After the party escapes, it is again possible to return to the temple.
If the player does not open the chest in Macalania Temple, defeating Dark Shiva is required to get Anima.
===Dark Bahamut===
After defeating Yunalesca and obtaining the airship, Dark Bahamut takes her place in the Zanarkand Dome. If the Sun Crest was not obtained before embarking on the airship, the only way to get it is by defeating Dark Bahamut.
===Dark Anima===
If the player returns to Mt. Gagazet after viewing the campfire scene at start of Zanarkand Ruins, and then completes Wakka's ball-throwing trial in the mountain cave once more, Dark Anima will appear at the entrance to the mountain. The party is not forced to fight Dark Anima, so she can be spawned and then left alone until the player is ready.
===Dark Yojimbo===
Leaving and reentering the Cavern of the Stolen Fayth after completing its events will summon Dark Yojimbo to ambush the party. After his first defeat, the summoner will retreat through the cavern, and the next battle will initiate upon their next encounter. Dark Yojimbo must be fought five times in a row for him to be truly defeated.
Returning to the save sphere to replenish the party's HP and MP and to save the game will not reset Dark Yojimbo's battle count, but if the player reloads their saved game using the soft reset, enters the blitzball menu, or leaves the cavern, the battle count is reset and the player must start over from the first Dark Yojimbo fight. This can be used to the player's advantage to fight him repeatedly to obtain the drops he provides.
===Dark Magus Sisters===
:For their battle information, see: Dark Sandy, Dark Mindy and Dark Cindy.
After obtaining the airship, the Dark Magus Sisters are found on the Mushroom Rock Road, near the exit to the Mi'ihen Highroad, and can be fought together or separately.
Once the Dark Magus Sisters are summoned, they will approach the party, and if they catch them, a battle against all three sisters will initiate with their Overdrive bar full. If the player avoids them and runs towards the valley, the Dark Magus Sisters will give chase. If the player reaches halfway up the valley, Dark Cindy will give up, and if the remaining two sisters catch the party, Dark Cindy will not participate and will be fought separately.
If the player reaches the mushroom elevator at the north end of the valley, Dark Mindy will give up the chase, and the player will face Dark Sandy on her own. Once Dark Sandy is defeated, the player must take the elevator back to battle Dark Mindy, and run back through the valley to fight Dark Cindy.
Fighting the three Dark Magus Sisters separately has many advantages, as the player can heal between battles, and the sisters cannot use their Delta Attack Overdrive, using Mega-Graviton instead.
The Dark Magus Sisters can be evaded by reaching the save sphere, saving and soft resetting. Upon reloading the game, Mushroom Rock Road can be traversed through as normal unless the player runs into the summoners again.
===Penance===
Once the player defeats the Dark Aeons, Penance will appear as an option on the destination selection screen on the Fahrenheit. It is a superboss unrelated to the Dark Aeons that boasts 12,000,000 HP for the main body, and 500,000 HP for the arms. 
==Etymology==
The word "dark" means "lacking or having very little light or color", as well being another way of saying "evil".
==Citations==
de:Schwarze Bestia
it:Eoni oscuri
Category:Final Fantasy X
Category:Superbosses
Category:Enemy families in Final Fantasy X