Inside Sin

Inside Sin, known as just Sin in the menu (but called Inside Sin at the Monster Arena) is a location in Final Fantasy X, and the game's final dungeon. It is located inside Sin, a gargantuan whale-like beast that threatens all life on Spira. This is the only storyline location that must be manually filled in by the player by traversing the area, highlighting its unknown nature.

Story
The final area of inside Sin, Dream's End, is briefly glimpsed when Tidus is first absorbed into Sin from Dream Zanarkand. He is teleported to Dream's End, where a vision of Jecht stands on the central platform. After Tidus "swims" toward the platform he is transported to the submerged ruins. Another section, the Nucleus, is seen in the aftermath of the disastrous Operation Mi'ihen, where the souls of Sin's victims can be seen wandering.

After summoner Yuna has abandoned her pilgrimage and decided not to let Yunalesca turn one of her guardians into the Final Aeon to defeat Sin, the party looks into new ways of tackling the beast. They decide to use the party's airship, Fahrenheit, to fight Sin in a way no one has ever attempted before.

When they penetrate Sin's armor, the party makes their way inside Sin and toward the center, where Yu Yevon rests. On their way deeper into the beast the party faces Seymour Guado, who has been absorbed by Sin, for a final battle after which Yuna sends him at last. At the center of the gargantuan beast, in Dream's End, the party meets Jecht who transforms into Braska's Final Aeon. After being vanquished, Yu Yevon's spirit seeks a new host and possesses Yuna's aeons one by one. The party defeats the aeons until Yu Yevon has no more host bodies to possess and then defeats Yu Yevon himself. Upon Yu Yevon's death he stops summoning Sin and it explodes above Bevelle, while the party escapes on their airship.

Locations
Most of the areas are based on the ancient Zanarkand except that it is a distraught projection of it.
 * Sea of Sorrow - A haunting, red-tinged sea winding through a cloudless vista, it is traversed through a series of waterfalls and watering blue platforms. There are symbols of Yevon surrounding this place.
 * Garden of Pain - A series of steps leading to a platform, it is where the battle with Seymour Omnis takes place. Once he has been defeated, this area is bypassed on all subsequent trips through Sin, but the staves will remain.
 * City of Dying Dreams - A maze of moving platforms and teleport glyphs which must be navigated. Various side paths lead to treasure chests containing weapons and items.
 * Tower of The Dead - As the player approaches what appears to be an exit to the city, a large metal tower descends and blocks their path. Examining a glyph on the side of the tower will teleport them past the point of no return and to the next area.
 * The Nucleus - A surreal environment of crystalline floors and walls; the goal is to touch the colored crystal orbs which appear in the area before they disappear. The camera angle is always moving, adding to the disorientation. An item is awarded each time a crystal is touched, but touching the icicles which sprout from the floor will cause a battle to begin. After touching ten crystals the player is transported to the next area. The area is briefly seen after Operation Mi'ihen's failure.
 * Dream's End - A ruined version of Zanarkand's blitzball stadium with a platform leading to the center of the arena. Here the party meets Jecht and fights Braska's Final Aeon. When it has been defeated, Yu Yevon reveals himself, searching for a new aeon to possess.

Treasure
In the City of Dying Dreams area, the player will find a glyph on the right wall. The first glyph tells the player to kill ten individual fiends. After doing so, return to the glyph and touch it to reveal another. The player must kill ten more to open the next door and then 15 to open the final one. A quick way to achieve this is to battle a party of three enemies (like Exoray's group). After the player has opened all three doors, they will find a chest with a Lv. 4 Key Sphere.


 * Special Sphere
 * Phantom Ring
 * Elixir
 * Wizard Lance
 * Lv. 3 Key Sphere
 * Lv. 4 Key Sphere (in locked room, after defeating 35 individual fiends in City of Dying Dreams area)
 * Four-on-One
 * Defending Bracer
 * Megalixir
 * 20,000 gil
 * HP Sphere
 * Defense Sphere
 * Laevatein

In The Nucleus area, small floating egg-like crystals appear alongside spike crystals popping out of the ground. The player must touch the floating crystals and avoid the spike crystals. The egg crystals disappear after a short time, so grab them quickly when they appear. Each one will give an item in a random order:
 * Hrunting
 * Mage's Staff
 * Prism Ball
 * Wicked Cait Sith
 * Knight Lance
 * Stillblade
 * Infinity
 * Attribute Sphere
 * Skill Sphere
 * Wht Magic Sphere

Enemy Formations
Sin= Note: The battles only occur if the player touches a spike crystal.
 * Sinspawn Genais, Sin (Boss)
 * -|Sea of Sorrow=
 * Ahriman x3
 * Exoray x2, Ahriman
 * Adamantoise
 * Gemini (sword), Gemini (club)
 * Behemoth King
 * -|Garden of Pain=
 * Seymour Omnis, Mortiphasm x4 (Boss)
 * -|City of Dying Dreams=
 * Exoray x2, Ahriman
 * Adamantoise
 * Gemini (sword), Gemini (club)
 * Behemoth King
 * Wraith
 * Demonolith
 * Great Malboro
 * Barbatos
 * -|The Nucleus=
 * Behemoth King
 * Wraith
 * Demonolith
 * Demonolith x3
 * Great Malboro (always Ambush battle)
 * Barbatos
 * Land Worm
 * Varuna
 * -|Dream's End=
 * Braska's Final Aeon, Yu Pagoda x2 (Boss)
 * -|Unknown=
 * Valefor, Yu Pagoda x2 (Boss)
 * Ifrit, Yu Pagoda x2 (Boss)
 * Ixion, Yu Pagoda x2 (Boss)
 * Shiva, Yu Pagoda x2 (Boss)
 * Bahamut, Yu Pagoda x2 (Boss)
 * Anima, Yu Pagoda x2 (Boss)
 * Yojimbo, Yu Pagoda x2 (Boss)
 * Cindy, Sandy, Mindy, Yu Pagoda x2 (Boss)
 * Yu Yevon, Yu Pagoda x2 (Final Boss)

Dissidia Final Fantasy
The Dream's End area is the representative arena of Final Fantasy X. Unlike most arenas, Dream's End is only used for the two fights against Jecht: one in Tidus's storyline and the other in Shade Impulse. No other bosses are fought at Dream's End, though a handful of cutscenes occur here, including Firion and the Onion Knight's respective conversations with Cosmos.

The arena consists of the ruined Zanarkand blitzball stadium surrounding a circular platform over a field of lava, which is treated as a banish trap. A massive replica of Jecht's sword appears on the central platform, much like after defeating Braska's Final Aeon in Final Fantasy X. Long grind bars run along the outer edge of the arena, connecting the central platform to the ruined "stands" on the opposite side. In the Ω version of the stage, every time a character guards, dodges, or lands an attack, the Bravery pool increases, and when damage is dealt it increases by an amount equal to the damage dealt.

The Moonflow is the battlegen item obtained through stage destruction in this area.

Dissidia 012 Final Fantasy
Dream's End returns. In the 12th cycle, Yuna faces off against the Emperor here after he struck down Tidus.

Theatrhythm Final Fantasy
Dream's End appears as the BMS for "Fight With Seymour" and "Otherworld". When playing "Fight With Seymour" during a Dark Note, the BMS featured is the Garden of Pain.

Theatrhythm Final Fantasy Curtain Call
Dream's End and the Garden of Pain return as the BMS for "Otherworld", "A Contest of Aeons", and "Fight With Seymour" respectively.

Musical Themes
The theme that plays inside Sin is "Twilight". "The Unsent Laugh" plays when the party discovers Seymour.

Trivia

 * The name of the area where the party fights the aeons and Yu Yevon is never revealed.

Dentro Sin