It looks like an infernal puzzle box. Normally its DC25 INT to figure out how to open it or you take something like 35 psychic damage on fail. Inside are the contracts between devils and others. Now, I am not sure about the destruction of these things in this game compared to D&D, but if the gith are looking for it they are bound by contract to Tiamat, one of the former Archdukes of Avernus until Asmodeus demoted her and put Bel in her place (who was then replaced by Zariel). I dont think the gith want to destroy it - i think they want to get it back so it isn't broken so they can keep their dragons.