[PC][2000s] mmo where you progressed through a tower’s floors

I played an mmo with my dad back in the 2010-2015 range where you progressed through floors in a tower dungeon. Each higher floor had harder enemies, but you could move between them freely. You could also party up with other players and I think that let you share XP.

1st or 3rd person (i don’t remember) but graphics were similar to dungeons and dragons online. I know it was fantasy themed as we didn’t play anything sci-fi in that era until SWTOR.

Based on talking to my dad it had to have been free, but I can’t find it anywhere online so please tell me i’m not hallucinating!