The Vazhappally Sasanam or Vazhappally inscription is said to be the oldest rock inscription of the Chera (Kulasekhara) kings (who had Mahodayapuram as their capital) discovered in the state. Some historians are of the view that the Thrikkakkara inscription is the oldest.
According to the inscription, the first Kulasekhara king was Rajasekharan. The inscription was written in the twelfth year (AD 830) of his rule. It says about the decision taken by the local rulers of the "nantuzhainadu" in the presence of Rajasekhara Perumal that those responsible for the failure to offer the nithyabali at the Thiruvattay temple should give "100 deenaram" fine to the Perumal. The inscription is cited as a proof for the command of the Perumal over local rulers.
The inscription provides valuable insights into the Kulasekhara dynasty. While other inscriptions begin as "Swasthisree", the Vazhappally inscription begins with "Namasivaya" and describes the king as "Parameswara Bhattarakan" which strengthens the assumption that Rajasekharan was a Lord Shiva devotee. There is a claim that Cheraman Perumal Nayanar, a Shaiva Sidha, and Rajesekharan are the same person.
The inscriptions discovered in the state that date back up to the eighth century are in the Vattezhuthu alphabet. But during this period, Sanskrit words were written in the Grantha alphabet.
The Vazhappally inscription begins with the wordings: "Namassivaya Sree Rajarajadhiraja Parameswara Bhattaraka Rajasekaradevarku". Though the Tamil alphabet became popular in Tamil Nadu by the eleventh century, Vattezhuthu alphabet was in use in Kerala till fifteenth century. The Grantha alphabet underwent modifications to become Arya alphabet in Kerala.
The Vazhappally inscription has a reference to Deenariyas coin which points to the existence of commercial relations between Kerala and the Roman empire during the period.