Final answer:
Emperor Leo VI offered up the "treasures" of the Church to the Emperor and was executed.
Step-by-step explanation:
The emperor who offered up the "treasures" of the Church to the Emperor and was executed was Emperor Leo VI. This act was seen as an atonement for his sin of marrying four times. However, some scholars debate whether the mosaic actually represents a specific historical emperor or is a more general representation of imperial submission to Christ.