Image - 

This is just the goop form. Their humanoid form is the same, just more humanoid (obviously lol) and they need a host for it. Also the puddle form is just a magenta puddle.

I also forgot to draw his translator in this image.

Gender - Bigender, they can be either female or male.

Fandom - None, Puri belongs to all universes. Though they should be used in the Undertale fandom.

Bio -  Puri was created in a lab, at sciencetale, they were labeled they were one of the first experiments that Sciencetale Gaster used many different soul traits for. At first, it was just a soul, but when they added a little puppy host, it took its form, and became a full liquid.
Sci!Gaster was so proud of his work, that he kept the little experiment in a metal room, and performed many tests on it everyday, sometimes letting them out for a walk, where they could see all the other experiments. One day the experiment got tired of all the experimenting and spoke to Sci! Gaster with the translator collar he had made them.
Sci!Gaster was sad that their experiment wanted to leave, so they decided to show them the core, their best work, to show the experiment that they were a piece of art. However they werent convinced and when given the opportunity, let Sci!Gaster fall to their demise.

 When  escaped the lab, they made their way to snowdin forest. They hid there for a week, living off of whatever they could find, one day as they were looking for food, they had tripped and fell off a cliff. At the last second teleported out of fear.
The next thing they knew they were in a purple bricked hall, tangled in vines, they heard someone humming nearby and tried to escape the vine, but they could not. A white goat monster in a purple robe came into the room. She was walking down the hall before she heard the experiments attempt to escape. She found them and freed them before taking them home, and renaming them Puri from the purring they gave when they fell asleep.

While Puri was asleep Toriel invited Frisk into her home. When Puri woke up, he heard some kind of fighting, and the smell of burning from the basement. When they became curious and checked it out, they came too late and saw Toriel shake before turning to dust infront of their eyes.
They couldn't believe it, and reacting fast, they went to run up to Toriel to try and save her, even though they knew her time was up. As he ran up to her, Frisk turned around with a smiled and slashed at Puri.
Their eyes widened in shock at the sudden pain before they teleported out of shock, leaving the universe they were just in.

Relations - 

Undertale Toriel - Who they view as their parental figure.

(From a roleplay) Sans - They met on a run where the human stayed in the ruins. After Puri accidentally killed Papyrus, Puri and Sans had a big fight, where Sans won because Puri did not want to harm Sans. In the end, Sans accepted Puri's apology, and let them teleport away almost half dead. He was the one who let Puri keep Papyrus's scarf. 

Dream - Puri met him on one of his runs to find a safe place. Dream said he found him by the extreme negativity levels coming off of him. Puri didn't really like him.

Sciencetale Sans - They both hate each other's guts for obvious reasons. 

Nightmare Sans - Puri came across him by accidentally getting too close to his castle and getting caught by Nightmare. Nightmare taught Puri of the BS and the SS. Nightmare and Puri are friends.

Jinx - Puri thinks Jinx is a bit too cheerful, so they try to push Jinx's buttons whenever they can.

Concept - Puri thinks Concept is okay. They provide them with their most valued resource but also wakes them up.

Benry - He is indifferent with Benry.

Misk - He thinks Misk is one of the cooler people he's meet.

Soul - Puri's soul is an upside-down heart that has a white outline, and in the middle of the Soul the colors Red, Yellow, And Green.

Likes - Dog Treats, Causing trouble, Warm Places, Cozy Houses, Beds, and Stardust.

Dislikes - Being touched, Being thought of as weak, doctor visits, labs.

Magic - Stop-Light Magic (I will explain it in the extra info)

Weapons -  Claws, Teeth, other types of magic they have taken in, and a Dagger.

Hobbies - Sleeping, Traveling the Multiverse, Causing trouble, Hiding.

Extra - The Stop-Light magic consists of 4 colors. Green, Yellow, Red, and Black. When Puri gets into a fight, their eyes turn green, then as they get more exhausted it turns to yellow, then to red, and when they have used all the magic that they can, their eyes turn black, and they fall asleep. Puri is scared of scientists and needles because of all the tests that were performed on them. Even though Puri is a dog, they purr very loudly when they feel safe or cozy.

Even though Puri is made of gooey substance, Puri's body is very physical, so they are not just a puddle, and their goop is very very very thick. So it is recommended you don't put your hand in their fur. Even though they are very soft, they don't like being touch, so you will get bitten and have your hand stuck.

☆