The sphinx is one of the four end-game bosses in Assassins Creed Odyssey that you need to kill for a piece of Eden as part of the Atlantis portion of your Odyssey, and although its undeniably the easiest of the four, its also the only one that asks you to keep the hacking and slashing to a minimum.
Instead, youre tasked with a classic test of wits and riddles to entertain the sphinx.
Source: N4G PC Assassins Creed Odyssey: How to find the Sphinx and solve its riddles