Silent Sparrow

Project Silent Sparrow is the name of portal that was build by Krei Tech as Alistair Krei tried to make science faction a reality on Akuma Island. Yokai planed to uses the portal to take everything that Alistair had build, before sending him into it.

Role in the film
Hiro Hamada saw Yokai bringing one of the three parts of the portal to San Fransokyo Bay, but had no idea what it was or the bird logo meant. After upgrading himself, his friends and Baymax, the team headed to Akuma Island and discovered the last part of it as they were trying to find Yokai. The team watched footage from the control pit and saw Alistair Krei demonstrating the portal to the garment.

There were two portals and as something went through one, it will out of the other. They had planed to send a human inside a pot through and out it, even when anomalies were showing in the scans, Krei still went with it to show that it was safe. But after the pot went in they lost contact with it and the second portal destroyed itself, while the other one became a vortex and sucked everything in.

The team's fiery of Krei being the masked man grew as they thought that "he" had stolen Hiro's Microbots as he could take his technology back, but Yokai ended up being Professor Robert Callaghan and he escaped with the end of portal when Baymax had his healthcare chip reasserted. After Hiro calmed out and the rest saw the rest of the footage, they realized why he wanted it: the pilot was his daughter, Abigail Callaghan and blamed Krei for sending her into it.

As Krei was opening his new Krei Tech Building, Callaghan used the microbots to capture Krei and to hold up the portal as it started to suck the building into it. Hiro later got the team to use the portal to their advantage as it sucks up the microbots. After Callaghen was catch the team went to find cover until the portal destroys itself, but Baymax picked up Abigail's life reading with in the portal, meaning that she was still. Hiro and Baymax went in to save her and discovered it's void universe, as parts of Krei Tech floating around it. After the two found Abigail and were about to bring her, Baymax's suit was damage and used his rocket fist (with his Healthcare chip clutched in it) to send when back. The portal then exploded as the two got safely.

Trivia

 * The portal's demonstration was set to open the film, with "Doctor" Robert Callaghan as it's creator, but the directors replaced it with the Bot Fight scene. They thought that it would be better if the audience discovering both the portal and the incident with the Hiro and his friends.
 * After the pilot went into the portal in the original layout of the scene, "something" came out of it.