To not confuse “obelisk” with “Obelix”, the word “obelisk” is a stone pillar of some sort. Obelix is a character. This kind of stone pillar narrows towards the end or gets narrower towards the end. It is tapering towards the end. Tapering simply means to get narrower.
I like this kind of stone pillar; I may even use the object in one of my writings but call it stone pillar. Or should I call it obelisk as that gives this kind of stone pillar definition. A simper way of saying this may be: The stone pillar, a monument to the world beneath the world, tapered upward, toward a narrow end, and stood proud among lesser stones and pillars.