Why is there dragon bones dungeon and costumes

Sawzallz

Eso Is before skyrim happens so why is there dragonbone dungeona and costumes maybe I'm wrong and eso happens after skyrim but that wouldn't be true because there isn't dragons in eso

Sigtric

It's not that there are no dragons during the time of ESO, there are. They are either 'dead' or in hiding. See the dead part for explanation of the word Bones in the title.

Ratzkifal

Most dragons are dead right now. There are only three exceptions with only one confirmed to be alive (Paarthurnax). The particular dragon from Dragonbones has been dead for a while now but a cult of Necromancers is trying to raise it to bring about the deadliest plague Tamriel has ever seen (I think). Not sure why they need the dragon for it, but perhaps it has a poisonous breath or something.

ESO takes place in the second era in the 200s, while Skyrim takes place at the beginning of the fourth era. There are roughly a thousand years between ESO and Skyrim, with Skyrim being the more recent event. The skeletons and dragon burial mounts are still here from long ago, long before even the events of ESO. You can see one in Kyne's grove south of Windhelm in Eastmarch.

That is the very same hill that you and Delphine encounter Alduin and witness him resurrecting the dragon burried there.