"All of Mercyful Fate's potential was fulfilled on Don't Break the Oath, a doomy, gothic collection of post-Priest/Maiden black metal preoccupied with Satan and the occult. Hank Shermann and Michael Denner keep their progressive rock tendencies reigned in while still delivering plenty of the neo-classical feel that gives the music its atmosphere, and King Diamond uses his vocal range to great theatrical effect. Fate's sound and attitude were highly influential on later gothic/black metal bands, especially in Europe, and Don't Break the Oath consistently encapsulates their appeal".