A complete mystery. Various states of "present" are believed to become compressed. Sorceress' power from many generations may cross over to give 1 sorceress great strength. No one knows what effect this may have on regular human beings.
Time compression is the concept of condensing all of time and space into a single moment, or "singularity". It can be initiated by the casting of a spell, which requires incredible power on behalf of the caster(s) and places them at the center of said singularity. By compressing the entire universe in this manner and placing herself at the center of it, Ultimecia would assimilate all of creation into herself, then use her sorceress power to recreate everything according to her desires. In the Japanese version, Ultimecia describes the time compression in a more detailed manner than in the English version, explaining the party's very existences will be absorbed by the time compression causing them agony as their thoughts would be ripped apart with their memories fading away leaving them unable to do, think or feel anything.
Laguna Loire, the president of Esthar, and Dr. Odine, come up with a plan for the SeeDs to venture to the future to stop Ultimecia. When Ultimecia compresses time, in the body of the Sorceress Adel of the distant past, the spell is halted halfway when Ellone sends Ultimecia's consciousness back to the future from whence it came. Ultimecia's spell affects time and space, an event which Squall and his SeeD party are relying on to reach Ultimecia's future and stop her before she can finish what she started.
When time and space begin to compress, Squall and his allies watch the world turn upside-down as a thousand different kinds of space from a thousand different points in time begin to fuse together all around them. The party must "swim" through the psychedelic landscape to reach Ultimecia. Because time and space are merging, moving through space allows the party to also move through time, and by utilizing this aspect of the halfway-completed time compression, the party emerges on the site of the old orphanage in the future.
In keeping with time compression's psychedelic nature, the party initially lands in a version of Edea's waiting hall in Deling City, wherein the atmosphere is foggier and there is a save point. When the party steps on the save point, dozen more spring up around the room, all of them illusions. At the center of this room the party fights a series of sorceresses from across time and space.
As explained by Laguna before the party departed, the only way for them to exist in a time they don't belong to, is to believe in each others' existence and to imagine themselves in the place they want to be alongside the people they want to be with. This is likely why the party emerges from the compressing time at the orphanage, the place everyone but Rinoa spent their early years. When the party flies through the compressing time Rinoa at first fears she will disappear, but Squall assures he won't let her.
The party finds Ultimecia Castle towering over the landscape in the desolate future world, and finds her from the clock tower. During the party's battle against Ultimecia her castle fades away as she begins absorbing time and space into herself, and during the final confrontation the party faces her in a dark void. Ultimecia's demise breaks the spell and the time begins to revert to its original form, but while the others make it back to their time Squall gets lost within the compressed time and almost disappears until Rinoa brings him back.
The world in disc 4 of Final Fantasy VIII is changed due to the effects of the time compression. Of the locations previously accessible in disc 3, most have become unreachable behind curtains of white light. The backyard of Edea's Orphanage is accessible, as are the Chocobo Forests and the Ragnarok for transportation. Trabia Canyon is still accessible as a foot passage through the Vienne Mountains between Trabia and the Mordred Plains.
The remaining accessible locations are home to Guardian Forces, which can still be claimed if they haven't been already: Centra Ruins (for Tonberry and Odin), the Deep Sea Research Center (for Bahamut and Eden), Tears' Point (for Doomtrain) and the Tomb of the Unknown King (for Brothers). The Fire Cavern also remains accessible.
Since disc 4 is occupied by only the final SeeD mission—invoking the time compression and vanquishing Ultimecia—the most important location of consequence is Ultimecia Castle. Four portals at the castle are linked to four corresponding portals scattered in the world: at Wilburn Hill in Galbadia, at Serengeti Plains in Centra, at Grandidi Forest in Esthar, and a fourth less-accessible one at Kashkabald Desert in Esthar near where Ragnarok has initially been landed in disc 4. This fourth portal (along with the Ragnarok) can only initially be reached by chocobo.
A flurry of attacks ending in one crushing blow.
Time Compression is Ultimecia's EX Burst. She freezes her opponent in place and conjures a swarm of magic bolts to bombard him or her. The EX Burst uses a slight variation of the mechanics used to execute Squall's Renzokuken, requiring the player to press in time with icons on a power meter to land up to twelve hits, compared to Squall, who presses to land eight hits. The finishing blow is an explosion called Sorceress Heart, paralleling the name of Squall's finishing blow, Lion Heart.
Compressing all of time is once again Ultimecia's goal, but her motives and the consequences vary. In Dissidia Final Fantasy she tells Squall she wishes to compress time to create her ideal world where she will be worshiped as a goddess-like being that can live forever, but in Dissidia 012 Final Fantasy her museum profile and speech to the Cloud of Darkness allude that time compression will allow Ultimecia to freeze time and kill all the other summoned warriors, leaving her to rule World B for herself.
The Omega version of Ultimecia's Castle undergoes time compression as a stage effect. When this occurs time rewinds, the gears of the arena spinning wildly to damage the Bravery of characters that touch them, and destroyed stage elements reforming. The stage Bravery also randomizes constantly.
Time Compression returns as Ultimecia's EX Burst. It has identical execution and power as in the original Dissidia.
The Time Compression effects of the Ultimecia's Castle stage also remain the same.
Time Compression is the special ability of Ultimecia's Dissidia card. For the discard of another Ultimecia card and three Water CP, Time Compression causes all Forwards other than Ultimecia to not become Active during the controller's next active phase.