Who invaded Charlemagnes empire after death?

After Charlemagne's death in 814, his empire faced invasions from several groups, most notably the Vikings, who raided coastal and riverine settlements. Additionally, the Magyars began to encroach from the east, while Muslim forces continued to threaten the southern borders of the empire. These invasions contributed to the fragmentation of Charlemagne's empire and the eventual rise of feudalism in Europe.