“Sufficeth” is just an old spelling of “suffices,” commonly used in the King James translation of the Bible and other Renaissance religious texts. People often use it in a joking manner to give their writing a semi-Biblical air, especially in the phrase “it sufficeth to say.” But they sound clumsy rather than clever when they omit the “it” and begin the phrase thus “Sufficeth to say. . . .” “Sufficeth” is a verb; it requires a subject.