Ceoseo

The lost cypher

A small, unassuming sign stood at the massive entrance into the continent of Tierras Mágicas:

Welcome (Or unwelcome) to Tierras Mágicas

Under the plain Latin alphabet writing, a different set of characters could be found forming the same sentence.
This ancient, lost cypher was known as Ceoseo, and was used by the inhabitants of Tierras Mágicas as well as their All-Mighty to hide messages.
The use was not widespread, but it was useful and at hand to all inhabitants when needed...

...Until it was not.

An alphabet and its cypher

Ceoseo consisted of an alphabet that took from the Latin one quite closely, with a few small changes: Irrelevant letters such as K were removed, while bothersomely nonexistent sounds such as CH were added.
On the reading side of things, each vowel of the alphabet translated to a different vowel of Spanish, while each consonant translated to a syllable, with some consistency on similarly-sounding consonants of the Latin alphabet.

The lost decoding sroll of Ceoseo

The entirety of Ceoseo was carefully noted down inside an ancient book by the Breath-of-Life All-Mighty for its preservation.
Later, though, he noticed how sometimes his writing books were lost, and decided his cypher was too precious to risk it like that.
So he ripped the piece out of the book, allowing the book to course its way in life, and took great care of preserving the cypher's scroll.
Not enough care, though, for the decoding scroll was lost forever, and the All-Mighty still has the original book, minus one page, in his possession.

Ceoseo sign for A by Naelín

The remains

Only two words of Ceoseo are remembered to this day.
The name by which everyone knows the Breath-of-Life All-Mighty was a direct translation of his original name, now dead and lost to the ages, of which only the cyiphered word Naelín is preserved.
The other is the cyphered translation of the word Ceoseo itself.
Of the alphabet, only the boring, all-too-similar letter for A is preserved.
It is thought that two other words, long and maybe even sufficient, lie dormant, preserved, as a small marginalia on a page among mountains and mountains of paper somewhere.
One day they may be revealed, and the cypher may be restored to a portion of its original glory.

Out of Universe note:
The author really wishes that the way he lost the cypher was fictional and/or exaggerated.