Chac is a an unsent boss from Final Fantasy X-2 who was formerly Lady Yunalesca. She is found in Via Infinito on the 80th floor. Chac is encountered later as a regular enemy on floors 81–84. Both forms can appear in Oversoul form.
Chac is a difficult enemy. She can petrify her enemies with her Stony Glare attack, which works regardless of immunities, but can be evaded with high Evasion and Luck stats. An ordinary Chac never uses Stony Glare if only one character is present. An Oversouled Chac, however, does not make such an exception. Chac can break a petrified character with her normal attack, removing them from battle.
Chac's ultimate attack, Heaven's Cataract, is used at any whim and does large damage to multiple characters, and can break them if they are petrified. As with all Basilisks, Chac does not use Heaven's Cataract in Oversoul form; instead she uses Stony Glare more frequently, which can be more dangerous, given Chac's agility.
The Oversoul attack pattern includes four additional attack types: Destroy Soft and Destroy Remedy, which respectively deduce one Soft and one Remedy from the player's inventory. They also do damage. When an Alchemist is present in the party, she uses normal attack instead. She can use MP Break to drain all of a character's MP. On characters at half health or below, the dummy Hunter's Gaze attack is sometimes used, which does no damage.
In the International + Last Mission and HD Remaster versions, the easiest way to deal with Chac is to drain her MP. If she has no MP, she cannot use her dangerous Heaven's Cataract move, and is thus helpless against a team of Berserkers with Evade & Counter. Draining her MP can be done in various ways, the easiest of which is by using a Soul Spring. Heaven's Cataract does not cost MP in the original version.
In the original version, an uncomplicated and effective way to defeat Chac involves bringing a Gunner in HP Critical condition who is wearing the Cat Nip accessory. Trigger Happy will deal in 9,999 damage per hit.
Equipping the Adamantite accessory to either a character wearing the Berserker or the Dark Knight dressphere can help survive Chac's powerful attacks; a downside is that the attack rate will be lower than usual.
Another strategy is to use three hasted Warriors using Delay Buster (only works on an Oversouled Chac), denying her from ever getting a turn. Chaining attacks on Chac also delays her turn; three fast Thieves, especially hasted (with Speed Bracers), can defeat her without her getting a chance to attack, as Thieves attack twice per Attack command, and if they attack one after another they build a continuous chain. This strategy can be used to unlock the trophy/achievement Full Chain in the HD Remaster version.
The player can set ATB mode to Active, ATB speed to fast, and have First Strike either from Thief's auto-ability, or the Highroad Winds/Mounted Assault Garment Grids. Yuna and Rikku can equip Strength-boosting accessories. For a specific strategy Yuna and Rikku can forgo Haste-giving accessories, while Paine equips Bloodlust and Wring, then replace Paine's accessories with Cat Nip and Haste Bangle/Speed Bracer. In the battle the player can try to time Yuna's and Rikku's normal attacks with Paine's to create a chain, with Paine as main damage dealer for her fast attack animation with Haste; Yuna's and Rikku's longer normal attack animations at normal speed keep Chac in stagger longer.
An easy way to defeat both normal and Oversoul versions of Chac is to bribe her with 1,751,400 gil in normal form, and 1,838,972 in Oversoul. The player can also bribe via Lady Luck's Slots without spending gil.
As Chac never uses Stony Glare if only one character is present, one can consider fighting Chac with a single character. Chac's non-Oversoul version's physical attacks can be dodged with the Berserker dressphere's Evade and Counter ability, making her Heaven's Cataract, which she uses at any whim, the sole move a single Berserker will have to fear. To avoid this, the Berserker can use a Soul Spring on Chac to disable her Heaven's Cataract move.
Another way to defeat Chac in the HD Remaster version is to capture Concherer and equip him with the Meggido Garment Grid. With the Key To Success and Ragnarok accessories, he gains massive stat boosts and Spellspring. The player should leave the Concherer's skills alone and level him up to about level 80. When the battle an ordinary Chac starts, Concherer will likely use his Gunk ability early on, eliminating the danger of Heaven's Cataract. If Chac is Oversouled, however, she can easily eliminate Concherer with Stony Glare. A similar strategy can be employed with Baralai due to his Looming Glacier ability (which also reduces an enemy's MP to 0), except that he would need to have Iron Dukes, Break Damage Limit, and Break HP Limit equipped.
Chac is recruitable into the party after the player defeats her in Via Infinito in Chapter 5. Chac cannot learn Stony Glare, but retains Heaven's Cataract and comes with Ailment Def. (complete immunity to status ailments) and Stonetouch.
Fiend Tale Edit
Another notable Chac was created from the spirit of a sailor's son who was among many who were killed by Sin, his village destroyed. Regardless, Chac ends up gaining a new family in fiends and teaching his adopted son what he learned from his father.