Author's note: to see the overview post on Maya gods and goddesses, go here.
God H -- Sak Nik (literally "white flower" a term used for the soul) -- is a god who may the god of a diversity of things. He used to be confused with another god (either termed God CH or God J), a god now understood to be the Hero Twin Xbalanque (Yax Balam).
The appearance of Sak Nik is of a young man. In the codices, he has a headband with flowers on it.
Sak Nik could be a god of music, the soul and/or the wind -- he is thought to be connected to the day Ik (meaning "wind"). Sak Nik may also be the god depicted in the "head glyph" variant for the number three (numbers could be written several ways, including with heads of gods). Another thing he may have been connected to is the Water-lily serpent -- a creature with a bird's head and snake's body with a headdress made of a lily and lily pad.
Beyond these things it is possible that Sak Nik was also god of music. In scenes found in the codicies in which the gods are making music, one of the most common gods in those scenes is Sak Nik.
In the codices, Sak Nik is possibly connected somehow with Itzamná (God D). Examples used as evidence include sections 12c and 15c of the Dresden Codex.
"Star Gods of the Maya: Astronomy in Art, Folklore, and Calendars"; Susan Milbrath; 2000
"Prehistoric Mesoamerica"; Richard E.W. Adams; 2005
"The Maya and Teotihuacan: Reinterpreting Early Classic Interaction"; Geoffrey E. Braswell; 2004
"Of Macaws and Men: Late Preclassic Cosmology and Political Ideology in Izapan-Style Monuments"; Julia Guernsey Kappelman; 1997
"To Be Like Gods: Dance in Ancient Maya Civilization"; Matthew G. Looper; 2009
"The Ancient Maya: New Perspectives"; Heather Irene McKillop; 2004