George Gemistos Plethon (1355–1452/1454 A.D.) was a Greek scholar of Neoplatonic philosophy. He re-introduced Plato's thoughts to Western Europe during the 1438 - 1439 Council of Florence, and was one of the chief pioneers of the revival of Greek learning in Western Europe. He was a follower of the Hellenic Gods and fought to have Them be worshipped again, like They had been in the past. He was a Humanist, and refused to absorb Plato’s dogmas into a Christian context, making him one of the first 'Pagan' Neo-Platonists.

Plethon--as he came to be known--had some strong ideas about how to re-establish this worship. Believing that the Peloponnesians, his people, were direct descendants of the ancient Hellenes, Plethon looked to re-create the Hellenistic civilization to far larger extends than just religiously. In his 1415 and 1418 pamphlets to this effect, he suggested ruler Manuel II and his son Theodore:
  • turn the peninsula into a cultural island with a new constitution of strongly centralised monarchy advised by a small body of middle-class educated men
  • the army must be composed only of professional native Greek soldiers, who would be supported by the taxpayers
  • 'helots' (an ancient term for Spartan slaves) would be exempt from military service
  • land was to be publicly owned, and a third of all produce given to the state fund; incentives would be given for cultivating virgin land.
  • trade would be regulated and the use of coinage limited, barter instead being encouraged; locally available products would be supported over imports.
  • mutilation as a punishment would be abolished, and chain gangs introduced
  • homosexuals would be burnt at the stake as sexual deviants
The political and social elements of his theories covered the creation of communities, government (he promoted benevolent monarchy as the most stable form), land ownership (land should be shared, rather than individually owned), social organisation, families, and divisions of sex and class. He believed that labourers should keep a third of their produce, and that soldiers should be professional. He held that love should be private not because it is shameful, but because it is sacred. Because of the Ottoman threat of his time, he also supported the reconciliation of the churches in order to secure Western Europe support. He also proposed more practical, immediate measures, such as rebuilding the Hexamilion, the ancient defensive wall across the Isthmus of Corinth, which had been breached by the Ottomans in 1423.

The new state religion was to be founded on a hierarchical pantheon of Pagan Gods, based largely upon the ideas of Humanism prevalent at the time, incorporating themes such as rationalism and logic. After his death, Pletho's Nómon singrafí (Νόμων συγγραφή) or Nómoi (Νόμοι "Book of Laws") was discovered, and it detailed his esoteric beliefs. He recommended religious rites and hymns to petition the classical gods, such as Zeus, whom he saw as universal principles and planetary powers. Man, as relative of the Gods, should strive towards good. His ethical system, overall, seemed to represented a merging of Stoic philosophy and Zoroastrian mysticism. Plethon believed the universe has no beginning or end in time, and being created perfect, nothing may be added to it. He rejected the concept of a brief reign of evil followed by perpetual happiness, and held that the human soul is reincarnated, directed by the gods into successive bodies to fulfil divine order. This same divine order, he believed, governed the organisation of bees, the foresight of ants and the dexterity of spiders, as well as the growth of plants, magnetic attraction, and the amalgamation of mercury and gold.

Plethon's pantheon varies greatly from earlier times. Zeus is the supreme sovereign, containing within himself all being in an undivided state; his eldest child, motherless, is Poseidon, who created the heavens and rules all below, ordaining order in the universe. Zeus' other children include an array of 'supercelestial' Gods, the Olympians and Tartareans, all motherless. Of these Hera is third in command after Poseidon, creatress and ruler of indestructible matter, and the mother by Zeus of the heavenly gods, demi-gods and spirits. The Olympians rule immortal life in the heavens, the Tartareans mortal life below, their leader Kronos ruling over mortality altogether. The eldest of the heavenly Gods is Helios, master of the heavens here and source of all mortal life on earth. The Gods are responsible for much good and no evil, and guide all life towards divine order. Plethon describes the creation of the universe as being perfect and outside of time, so that the universe remains eternal, without beginning or end. The soul of man, like the Gods is immortal and essentially good, and is reincarnated in successive mortal bodies for eternity at the direction of the Gods. [Wikipedia]

Needless to say, Plethon's ideas aren't Traditional; they aren't even Hellenic, but they have had a great impact on the way Neo-Platonic thought ingrained in society, and on the views of later generations on the ancient Hellenes. Surviving from his work is also a collection of hymns to the Gods of his pantheon. According to translator Manuela Simeoni:

"[These] hymns must be chanted at wake up, at midday and at sunset. This must be preceded by an announcement made by a ‘sacred herald’ chosen among the venerable ones of the community: "Listen, you all who honour the divinity; it’s time to address to the Gods the morning [or midday, or evening] prayer. Let’s call the Gods with all our heart, all our spirit, all our soul; let’s invoke them all, but above all Zeus who rules on them". What follows is a complex choreography in which all members kneel invoking the Gods, then put their right hand on the ground and lift a knee, continuing to recite invocations, then put the other hand on the ground and finally lay on the ground invoking "Zeus the king".
After invocation and before hymns, in this complicated ritual some ‘allocutions’ are also recited: these are some sort of prayers in which a divinity is thanked and the philosophic view of mythology is explained. They resemble a catechism that must be recited every day: there’s an allocution for the morning, three for midday and one for the evening. After the allocutions, hymns are chanted but not chosen randomly: first the monthly hymn, then the hymn that fits the celebration of the day and last but not least the all-year hymn to Zeus. In some particular days, they are preceded by the sacred hymn for the occasion."

The full list of hymns can be found here, and although Plethon's ideas aren't Hellenic, and very much non-Traditional, his hymns are quite beautiful. They can be a resource for anyone looking to extend their practice or simply their collection of hymns. I'll leave you with a snippet from the All Year Hymn To The Gods, in the hope that you will find beauty in it. Plethon's hymns are not part of my personal practice, but I love reading them because of the true devotion they portray.
"But, Gods, you who address the mind that leads us
and that you put on us similar to yourselves,
let us lead our life well in everything
and chant with you the supreme Zeus."