Kyrnyn was a cleric of Heironeous the party met and saved in Codex II. He had been polymorphed by the evil wizard Stondylus several years ago and turned into a two-headed ettin. Over time, the other head began to assert itself, calling itself "Muck" and taking control of the body when awake. It began attacking the local hamlet, and the party was sent to slay it. They managed to learn the meaning behind a riddle/poem granted to Heironeous to Kyrnyn. Realizing the error of his ways, Kyrnyn was finally granted a Dispel Magic spell, and was able to return to his human self and slay Muck.

The clues about the riddle directly from the pre-made campaign the DM used were as follows:

The riddle Kyrnyn has been tasked to solve is full of clues, but recognizing them requires an under- standing of Heironeous. The clues hidden in the riddle are explained below:
“Two heads have we, but born with one.”
(This identifies “we” as Kyrnyn, and indicates that he was born with only one head—thus, he was not always an ettin.)
“We avenged, healed, and protected.”
(This is almost directly quoted from the descrip- tion of good clerics in the Player’s Handbook. It is a clue that the speaker was once a good cleric.)
“Our master was Invincible,” (Heironeous’s title is “the Invincible,” indicating
that the cleric was devoted to Heironeous.)
“But punished we all who objected.”
(This is a bit more obscure. It relates how Kyrnyn abused his power as a cleric to exact vengeance, rather than justice. The adventurers are only likely to learn this if they convince Kyrnyn to tell them about his past.)
“Heeded we the six-armed king,”
(This is a reference to Hextor, Heironeous’s brother and arch-enemy—a deity with six arms. Hextor is the god of tyranny—a trap into which Kyrnyn had started to fall.)
“And so by our god were rejected.”
(This part Kyrnyn has already deciphered: Because he transgressed against Heironeous by behaving contrary to his alignment, he has fallen from Heiro- neous’s favor—as evidenced by the choice of divine spells Heironeous has allowed Kyrnyn.)
“Thus, this is our fate:
One head, twice bisected.”
(And so, Kyrnyn, who was already of two minds— one that served Heironeous, and one that felt it was acceptable to punish anyone with differing views— was cursed with two heads: one that serves Heiro- neous, and one that is more self-centered and tyran- nical.)