This build allows insanely fast AOE attacks while moving Sion across the map very fast even without boots. He will be able to chase down anyone with this build and the tenacity helps aswell because he can be easily countered with it. The build also allows high crit chance for even stronger basic attacks. I have changed the build a few times and this way seems to work the best even though you can go higher damage with less attack speed but forfeiting movement speed.