EntropyTale's iterations can be treated either as a
(It. 1) Frisk's home timeline, as described above.
Six dead Fallen Humans can be found Underground.
Seven dead Fallen Humans can be found.
Seven dead humans can be found, as well as the dust of several monsters.
A group of hostile monsters is found, the first major divergence. It is revealed that long ago, humans demanded that monsters put their prisoners Underground in distrust and fear of them, and seal them down with a barrier.
(It. 6) Many more monsters, many falsely accused, could be found Underground.
All monsters are entrapped Underground. King Asriel, Princess Hope and the Royal Scientist Gaster as well as the Chief of the Royal Guard Undyne do not attack Frisk, as they hadn't instated an anti-human policy.
Frisk finds Hope Dreemurr, Asriel's daughter, in the Ruins, and learned that Asriel was forced to implement an anti-human policy. Hope now strongly dislikes her father, and the monsters attack Frisk.
Gaster no longer is alive. No Royal Scientist replaces him. Monsters Sans and Papyrus can be found in Snowdin. Hope was learned to have died before the events of this iteration.
(It. 10); A Flower named Flowey appears outside the RUINs and at the End. Alphys is the Royal Scientist. Mettaton now has a body and is a star. Asriel is no longer King, and Toriel inhabits the RUINs and Asgore takes the reign as King. This iteration is what we know as UNDERTALE, except very minor differences in dialogue.
It is revealed that Flowey can remember the Resets. Toriel seems less confident. Asgore is much easier to defeat. Alphys is too shy and does not appear in the Pacifist Route.
Toriel rebelled against Asgore, and has a following of monsters which help her protect against him.
Asgore and Toriel have conflicting nations, Toriel being the Queen of the Kingdom of Free Monsters, and Asgore being King of the Kingdom of Monsters. On Toriel's side is Mettaton, Sans, Papyrus, and Alphys, and Asgore's side has Undyne, the Royal Guard, Muffet, and Flowey.
(It. 14); Asgore is let to rule, but has much of the Underground under quarantine from a virus.
The Underground is full of dust. Very few monsters are found alive and survived from the virus, including: Napstablook, Grillby, Mettaton, Alphys (in self-preservation), Annoying Dog, Flowey, Temmie, and likely a few others.
(It. 16); The same as the last iteration, however, this iteration begins the trend that monsters' bodies do not turn to dust when they die. Bodies lay everywhere. Flowey comments that this seems like it happens "only in spite of you" and that the universe is mocking the protagonist.
Flowey was able to get the Six SOULs and now has complete and utter control over the Underground. He is like a literal God, able to manipulate reality, bring people back from death, and so forth. Begins with an illusion by Flowey to mock Frisk.
(It. 18); Flowey still has the Six SOULs. However, in this iteration, Flowey has become King of the Underground and is worshipped like a God. Flowey takes refuge in Papyrus' empty husk. Sans, Alphys, Undyne, Mettaton, and others resist Flowey's rule in the Hotland Labs.
(It. 19); Toriel, Asgore, Muffet, Undyne, Gaster, and Flowey each have their own individual Kingdoms in the Underground. Monsters in general are more noticeably aggressive than previous iterations.
Iteration 20 Edit
The Kingdom is united under the rule of Asgore, who is a fierce dictator.
(It. 21); All monsters have their alignments switched. Comparable to Underfell, and rather similar, though minor differences.
(It. 22); The monsters seem much less inherently volatile, curiously, and are back to their usual state. However, many monsters in the Underground are infected by a virus caused by the escaped Amalgamates, making many monsters melting zombie-type creatures.
(It. 23); Monsters are infected by a different virus, making them very much like zombies, although they are not dead in such a state. They simply hunger for flesh. It is comparable to HorrorTale and AxeTale, however significantly different in multiple ways as well.
(It. 24); Monsters are beasts, and not the usual intelligent species seen in other iterations. They are creatures that follow mostly primal instinct, though many are kind and have morals, as well as understand language. Some can even speak.
(It. 25); Monsters are monsters in the human meaning of the word. They are horrid creatures, often bent on killing and death. Some are just vicious and rabid, and some are intelligent and conniving. Others aren't very evil.
(It. 26); When Gaster fell into the Void, an explosion occurred. Instead of Gaster falling into the Void, the Void fell into the world. Gaster now lives in a calm, structured and, albeit vacant, pocket universe. The universe he fell from, however, is in chaos, glitching and ebbing in and out of separate timelines. Inspired partially by Errortale.
Iteration 27 and Forward Edit
Unknown/Undecided/Undiscovered as of yet.