Long household

It didn't take long before the Carnage Portal stabilized. The deaths happening in its perimeter feed the portal, expanding and stabilizing it. 

A Carnage Portal was comparable to the bridge anchored by the Nest. The most significant differences were that a Carnage Portal was a temporary bridge, that it could only be manifested in the vicinity of recent deaths, and that the surrounding deaths fed it. 

Producing the Carnage Portal connecting from the inner regions of the Origin was expensive. Even the death of tens of millions wouldn't be enough to maintain the Carnage Portal for long. That factor, as well as the massive amount of energy required to teleport someone through the Carnage Portal, were the only reasons Eren could maintain his composure. 

He knew who would emerge from the Carnage Portal.