A few individuals and myself started up our own server that one person has connected with their provider. We play in normal survival and have gone to all islands surrounding the one we create our buildings on. We have found one illager outpost and fought it, along with handfuls of raids in our own island area since we keep villagers there for trades. After a few days of this, we were looking for the end portal after fighting a new raid where a Ravager or the illager killed with it dropped a book and quill with coordinates to a "basecamp". That was already strange since they aren't supposed to drop items. We figured we would explore that another day and went on trying to find the end portal, but leaving our island and only going a couple chunks away, the Basecamp loaded. There were pillagers, evokers, etc. and a massive tower and wall blocking the little illager buildings (resembling villager towns but with iron bars and the dark wood instead) into a part of a mountain. We raided the area and found command blocks spawning some of the illagers. There was also a mineshaft that teleported us into a cave with lava, wither skeletons, and even an illusionist that none of us had spawned into the game. We could not kill the illusionist and the teleport was very buggy since we would land in different spots each time. None of us had spawned in the command blocks either.
What is this? Is there something up with our seed that shouldn't have happened?
Are you sure the server isn't modified and has plugins?