Both the primordial soul wizard and the Dark Elf Mistress were genuine level 6 experts.
How could Levi guess their methods?
Therefore, Levi planned to use this opportunity to let those guys test the waters first.
If there were no problems, he would pay a visit and snatch it back.
If there was a problem, then he could avoid a disaster.
In short, to Levi, the remains and roots were not necessities.
Even if he didn't get it in the end, he wouldn't regret it. At most, he would feel a little regretful.
After finishing all of this, Levi left the Dark Elf Forest and found a barren mountain range to hide himself and the transcendent creatures.
He opened the Teatime Round Table and pulled the Blood Knights who were training in the Dusk Holy Temple over.