This metal shard appears to be part of an arrowhead. It hums with divine energy. You guess there are four other such shards in existence, assuming the other shards are similar sizes. The first time you touch the shard, you hear maniacal laughter in your head and must succeed a DC 16 Charisma saving throw or suffer a short-term madness effect (see “Madness” in DMG chapter 8).
Upon further investigation, you realize this shard belongs to the arrowhead that slew Xenagos, god of revels. The arrowhead is said to have shattered into countless pieces, though you can feel that the shard is longing to be reunited, perhaps under the influence of what essence remains of Xenagos. Should all the pieces reassemble, the arrowhead could be used as the focus of a revelrous ceremony that resurrects the fallen god. Remaining adherents of Xenagos or creatures seeking to overthrow the current pantheon would go to any length to recover it from you.