If using this in a build based around summoning it with the above card, "Belial - Marquis of Darkness" can be an alternative way to protect it from being targeted, while Sinister Yorishiro will save it once from destruction.
In any other scenario, "Safe Zone" and/or "Imperial Custom" can be effective in keeping Majesty's Fiend on the field for long enough to gain advantage.
Another card that can backup this one is "Dark Ruler Ha Des". Since effect negation caused by Ha Des follows the monsters to the graveyard, even if Majesty's Fiend leaves the field, those monsters are still unable to activate their effects.
Remember that this card wont stop continuous monster effects, so it could be paired with monsters whose continuous effects compliment any variation of a lock, such as "Banisher of the Radiance" or "Invader of Darkness".
Seeing how most decks rely on monster effects to do anything, using "March of the Monarchs" with this card can shut down many builds. This card even bypasses the protection of your opponent's "Constellar Belt", since it is not negating effects but preventing them from activating.
This card can even stop monster activations from the hand and graveyard, such as "Honest", and cards like "Necro Gardna".