(Creative, just for fun) What could have come through the breach?

Context: My players are undead (with the exception of one who is still lives). In their last encounter they angered the main god of my setting. A mortal who became a god, killed a bunch of the other gods and sent the rest into hiding (yeah Kratos rip off I know). He despises undead and began hammering on the Planar Wards (the barrier that keeps the different planes from merging) in order to intervene on the encounter.

He did end up succeeding and was able to get enough of his power through the Wards and possess a child, who then went on to explode on our paladin's face.

Now many other things could have crept through to the mortal plane in the few moments that the Planar Wards were breached. What kind of fun extraplanar denizens would you throw at the party in this situation?

I already have a few ideas of angels making their way through the breach to harass the party as well as some kind of avatar of the warlock's GOO patron.

There are 7 players in the party at level 6.