What was the Tumor and what did it do?

The Tumor was a massive bomb at the center of the full-prototyped Battlefield in the beta kids’ session. Rose speculates that the bomb is present in all null sessions or that it’s a mutation specific to their session. It’s unlikely that the bomb has anything to do with their Bilious Slick having cancer since the pre-scratch trolls also had a Tumor-like object and their universe was cancer-free.