The Shard of Accountability (5E)

From the introduction: During a celebration such as a birthday, PCs notice a mysterious package nearby: a giftbox ornately decorated with gold and silver gilded paper. A singular vellum note reads, “In eternal gratitude, may your paths always be illuminated by the light of Truth.” The gift itself is otherworldly and contains an artifact: the Shard of Accountability. It has been secretly sent by a lawful or good deity as a test.