Frisk is given a voice and personality based upon the player's actions in the game.

Others may refuse to help if they’re not a genocidal maniac.

Some may react negatively and refuse to help Frisk with world quests if they’re an extremely violent individual.

Each follower will have unique dialog banter and attacks. Frisk can only have either one Sans or one Papyrus with them.

Once said Echo is beaten that universe’s Sans (if applicable) & Papyrus (if applicable) or other character (if applicable) will follow Frisk back to UNDERFELL’s Underground, and Frisk will be allowed to recruit them to undertake world quests - they are known as Echo followers.

Once Error is stopped in that Echo, he will move to another, and so on. Each Echo will have around 30 minutes to an hour of playability depending on its complexity with varying difficulty levels.

Echoes will bring Frisk to different alternate universes, such as Nextale, Underswap, and Naturetale, this list will be expanded as time goes on.

Once this is out of the way Frisk will be ready to embark. Ink!Sans will explain that the entity known as Error is destroying alternate universes, and he must be stopped before he brings about complete and utter annihilation.

After Frisk's gear is at an acceptable upgrade level, they will be approached by Ink!Sans, since they are the true, original Frisk.

When the player initially beats UNDERFELL, they will be prompted to undertake world quests to stop a mysterious entity that has appeared in the world of UNDERFELL, in order to upgrade their gear.

An “ Echo” is a concept that is being implemented as UNDERFELL’s endgame.

Upgrading weapons and armor will allow to tackle harder echoes and difficult bosses which would otherwise be impossible without improved equipment.

After this, Frisk can upgrade their weapon’s attack and armor’s defense further with upgrade tokens.

All weapons and armor will automatically scale to the highest attack/highest defense value weapon/armor in the game once the main story-line has been completed.

Once the player finishes the game, they can embark on World Quests with either Sans or Papyrus and collect Upgrade Tokens for their weapons and armor.

Everything suddenly changes as Frisk is helping the monsters move above ground to live among the humans and it’s up to Flowey, Sans & Papyrus to get Frisk back to their original reality, if they can. UNDERFELL takes place directly after Frisk completes a pacifist run from the original UNDERTALE.

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