Staak is a bio-organism that is one of the Empire's Evolvers who are the ultimate assassins of the Kree race. Such agents are normally encountered in pairs with Staak being paired with her Kree-kowl steed. Both are typically in the form of blue eggs that are injested by a host whereupon they emerge after being expelled from their victim. Staak's emergence came on Earth where a group of Kree attempted to lay claim to an infant Watcher and she came into formation after being expelled from the body of Benjamin Grimm. This came when the Kree agents came into confrontation with the Skrulls under the command of Paibok the Power Skrull. Once expelled, she quickly grew to maturity where she exclaimed that she had been charged by the Kree and the Supreme Intelligence with the eradication of the Earthling known as the Thing. She would battle both the Thing and the Skrulls until her Kree-kowl also reached maturity. However, Grimm shattered her power staff that began the reversion process that turned Staak back into her egg-like state along with her kowl that were thrown by Grimm to the defeated Kree who departed the planet.
Until she has been ingested, Staak exists in the form of an egg. After ingestion, she emerges from the victim fully-grown with armor and a staff. Once the staff is broken, she will revert to an egg form.