This is a low-poly background building, that shows up in some early levels of the game and in a few cutscenes in Hextech Mayhem. It is a prominent landmark building in the city of Piltover. There's also some various low-poly golden background monuments as well, typically seen around the University area.
Modeled in Maya, textured in Substance Painter.
Heimerdinger model by Josh Defries: https://www.artstation.com/artwork/zD0yvm