Mysterious Monolith

Here's what happened-
Any creature around the area would have witnessed the ground shake, cracks formed in the ground with green energy pulsing from below. A pulse surged through the ground at a steadily increasing rate at and expanding until the ground became loose and each pulse was more forceful than the last. As the radius of the zone became wider, the banging got louder and louder. 

The air would start to tear until as the dimensional border was being assaulted until finally, the object broke through like a battering ram and rose out of the resulting rift into your world. The dimensional wall would naturally start to repair itself, filling in the gap and the monolith remained on this side of the portal. All that made it through the portal was now grafted into this realm's environment. 

The twisting spire of alien rock had strange designs carved into it, Whether it was heiroglyphics or maybe even runes they were symbols not of any known Overworld language. When it first arrived the Monolith was glowing green from within but over time the light has faded until it goes completely dark. While inert, one could examine that the stone had a luster similar to quartz. Much of the base and foundation of the structure was buried under the rubble created from the hole being punched through the veil. From miles away you can hear the Monolith  thrumming from wind blowing on and through it, making different sound patterns depending on the weather.