I have been modeling a dragon, and I see all sorts of artifacts in the mesh. When I go into edit mode and select all by trait, blender says they are non manifold and interior faces. I have researched many different ways of fixing bad geometry such as merge by distance, Weld modifier, and trying to smooth or use other tools in sculpt mode.
The resulting mesh will have a throughout higher density and i do not know if you want to retopologize your dragon, as that might be the best way to reduce the density again.
I tried to use the decimate modifier and it actually resulted in similar artifacts, so retopo seems to be the best choice.
Another option going out from the version you shared, would be to cut away half of the dragon and using the mirror modifier. Then you would have to go over half the dragon and manually remove all the overlapping faces, believe me, it will be a good timekiller. Retopo seems in my humble opinion to be the better option.