This is possibly a slime mold which starts off with egg-like structures similar to those in your photo. It grows on decaying organic matter in damp conditions. I suspect the monstera has been sitting for some time in a tray with at least a little water left in it. I would start by cutting off all the roots growing out of the pot and repot the plant into another one slightly larger. Water thoroughly and make sure the water drains completely so that there is none left for long in the tray.