ALTJIRA

Real Name: Altjira

Identity/Class: Aboriginal god

Occupation: God of Dreamtime

Group Membership: Aboriginal Gods, Council of Godheads

Affiliations: Aborigines, Ajak, Athena, Amadeus Cho, Hercules, Longshot, Mikaboshi, Snowbird

Enemies: Vali Halfling, Kly'bn, Sl'gur't

Known Relatives: several unnamed wives and daughters

Aliases: "Dreamwalk", Sky-Dweller, All-Father

Base of Operations: Alchera and the "Top of the Sky"

First Appearance: Marvel Comics Presents I#16 (early April, 1989)

Powers/Abilities: Altjira showed the ability to shape-shift. He seemingly appeared while people were asleep and liked to cause chaos. He possessed many other powers as a god, but they were not yet shown.

(Marvel Comics Presents I#16/3) - By the instructions of an Aborigine the X-Men Longshot tried to enter the Dreamtime. Longshot fell asleep and the creature slapped him. Longshot was surprised and listened to the gurgling sounds of the creature. It began to run and Longshot followed it through the house. The creature hit Longshot with a plank over the head and began to throw stuff at him. Longshot played along and threw stuff after the creature as well. The creature grew wings and retreated. It hid behind a corner while Wolverine-like claws grew out of its hands. It attacked Longshot again and they continued to tarnish everything in the house. The creature knocked out Longshot, and he fell down the stairway where he was found sleeping by the other X-Men when they returned. The creature was gone.

(Incredible Hercules#116-117) - Altjira was among the gods summoned to join the Council of Godheads by Athena. As Athena prepared a force of gods led by Hercules to confront the Skrullian gods, Altjira contributed to the mission a vessel made within the Dreamtime and composed of the skin worn by the Rainbow Serpent. Aboard this vessel, Hercules' forces were able to travel within the Dreamtime to where the Skrullian gods dwelled.

(Heroic Age: Prince of Power#2) - Altjira was present at the Chamber of the Council Elite (Council of Godheads) when Vali Halfling contacted and threatened them after gaining the second item he needed to gain omniscience and the power to overthrow all gods.

Comments: Created by Ann Nocenti, Larry Dixon & Alfredo Alcala.

What was this creature?

My favorite possibility for this character is that it was Altjira as seen above in the possibilities.
The sky father of the Aranda tribes of Central Australia, Altjira is looked on as the god of the Alchera, the dream time. It is said that he made the Earth, then retired to the top of the sky, and is now indifferent to mankind. He is represented as a man with the feet of an emu, while his wives and daughters have the feet of dogs. Also called Sky-Dweller or All-Father.
--Will U
Let's compare the god with this story's creature: Both lived in Australia and seemingly in the same area! Both had something to do with the Dreamtime! Both possessed emu feet!
 Enough proof for me, but there were still other more boring possibilities.

The far less interesting and less likely possibility would be that this creature was a creation of Orphan (surely not intended by Nocenti as Orphan was created a few years later).

Another possibility would be that Longshot was just hallucinating the creature while dream walking and destroying everything in the house.