Basalt Pillar is an elemental stone used for ascending characters in Genshin Impact. Find out more about how to get and where to find this character ascension material on this page.
A pillar form by the shell of a Geo Hypostasis. It is composed of high-density Geo energy. This is the heaviest component of a Geo Element. Maybe the reason a Geo Hypostasis creates this polar out of its shell and raises itself is just to get closer to the sky, not to combat enemies.
How To Get Basalt Pillar
Basalt Pillar is obtainable as a guaranteed reward from defeating a level 30+ Geo Hypostasis.