What is yomotsumono?

Some articles on yomotsumono:

The Great Yokai War - Plot
... his revenge, Kato allies himself with a Yokai named Agi while he summons a fiery spirit called Yomotsumono, composed of the resentment of the many things which mankind has ... With Yomotsumono's flames, Kato feeds it Yokai which are used as ingredients in creating violent junkyard Tsukumogami under his control that capture other Yokai to build their numbers while killing ... is called back by Kato to begin the final phase by joining with Yomotsumono ...