It's not like spells and traps got any less powerful over the last fourteen years, but monsters have come a long way since those days. Just about all monsters that see play incorporate some aspect of an otherwise already printed spell or trap. Bujin Yamato's an interesting fusion of Reinforcement of the Army-like search cards and Foolish Burial. Mobius the Mega Monarch is literally three Mystical Space Typhoon if you don't Tribute a Water monster, and three Night Beam if you do. Thestalos the Mega Monarch is a walking Confiscation with a variable number of Sparks and a Meteor of Destruction tacked on, seemingly for the funsies. Each of the Dragon Rulers Monster Reborn themselves, and then respectively pick up additional effects just because. Psychokinesis is arguably one of the best spot-removal cards the game's ever seen, but having to keep a Psychic on board to use it can be rough; Number 61: Volcasaurus and the Atlanteans find that amusing at best, just to name a few cards with the ability to shoot away whatever.
There've been a handful of effect-negating cards over the years to help deal with that, like Skill Drain and Effect Veiler, but they all have a blind spot in what they negate. Monsters that leave the field dodge Skill Drain and Fiendish Chain in every case, and Effect Veiler in most cases. Light-Imprisoning Mirror and Shadow-Imprisoning Mirror don't help against effects that activate in the hand or while they're banished, and only hit one attribute each. With Primal Origins we were given a new weapon against effect monsters that's practically unrivaled in power and coverage: Majesty's Fiend.Recognizing Greatness
Even though Majesty's Fiend has no equal overall, there was actually another card with nearly the same effect released several years ago. When Light of Destruction came out, Angel O7 came with it, which is virtually identical to Majesty's Fiend. Angel O7 can be Special Summoned, unlike Majesty's Fiend, but if you Summon it like that you don't get its effect. The problem was that you had to Tribute two monsters for Angel 07, which is largely absurd. Not impossible by any means, but also not wise or reliable. Majesty's Fiend is only 100 ATK smaller and does the same thing for a single Tribute, which is immensely more reasonable.
Since you can't Special Summon Majesty's Fiend, you're basically left to rely on your ability to Tribute Summon. In that regard, Treeborn Frog can seem like the automatic answer, but there are other options. While you're dealing with floodgate cards like Majesty's Fiend, playing more defensively should be your goal. Soul Exchange may not seem very defensive up front, but it's basically monster removal that lets you drop Majesty's Fiend onto the field for free. If you can 1-for-1 a Tribute Summon, you're doing it right, and as long as we're going into things with that mentality, giving up a single battle phase isn't such a bad trade. Realistically, if you were to Tribute your own monster to Summon it, the most ideal use for that battle phase would be to kill something in battle anyway, which you just did, sort of.
There's actually another reason to look outside of the Frog engine for Majesty's Fiend: Return of the Monarchs can search for it. It has the same properties as a Monarch by stats, being Level 6, 2400 ATK, 1000 DEF, and that's all Return needs to grab it from the deck. You can only search when you Tribute Summon, but a deck that uses Return, Soul Exchange and Majesty's Fiend is probably going to be doing that at least somewhat regularly. More specifically, you should be Tribute Summoning as a 1-for-1 or +1 frequently, probably through the actual Monarchs and Mega Monarchs, making Majesty's Fiend even more lethal when it hits the field. Ripping into your opponent's backrow with Mega Mobius or their hand with Mega Thestalos and then shutting off their ability to fight their way back into the game is basically a victory in most respects.
While it doesn't have any actual defenses, it's worth noting that Traptrix Trap Hole Nightmare's been quite popular lately, and Majesty's Fiend dodges it. It doesn't have any activating effects at all, just like Jinzo or Great Shogun Shien, so it can hit the field and get to work without worrying about that specific pitfall. In the same vein it also doesn't stop other continuous effects; Majesty's Fiend only stops the activations of things.Exemplifying Grace
Lightsworn are getting pretty popular right now, with the Lightsworn Structure Deck dropping three new monsters into their ranks. Minerva, Lightsworn Maiden; Raiden, Hand of the Lightsworn; and Michael, the Arch-Lightsworn all landed in the TCG and people are picking up the deck again left and right. Unfortunately, Majesty's Fiend really can't stand milling, so it turns off all that noise. In fact, the only way a pure Lightsworn deck could even kill Majesty's Fiend is to drop Judgment Dragon and run it over in battle. If you have any backrow to protect Majesty's Fiend, that's almost the definition of a free win.
The same could be said for Sylvans, which tend to run just about zero traps whatsoever. Other than some gnarly-strong spells, the entirety of the Sylvan game plan is to rush their vine-y dominance onto the field and control the board with powerful monster effects. Orea, the Sylvan High Arbiter is more or less a roidrage Madolche Queen Tiaramisu, throwing up to three cards back into your hand and stacking up to eight cards from your opponent's deck so they know what they're drawing and what they'll be excavating. It's not their only play, but it's one of their best, and Majesty's Fiend isn't inclined to care. Other than the high ATK they have access to in the Extra Deck, they're harmless. Beyond that, they can't really get to the Extra Deck without monster effects in the first place.
Most Mermails decks are in the same boat, running a small number of traps, mostly which have nothing to do with killing monsters. They're a little more frightening thanks to Abyss-sphere's ability to snag monsters from the deck and run Majesty's Fiend over in battle, or Soul Charging into the Extra Deck for some muscle, but there are ways to keep that at bay. Forcing your opponent to use Abyss-sphere aggressively like that makes your Mystical Space Typhoon about a million times better, since you can chain it and put an end to whatever your opponent thought was about to happen. Not to mention Soul Charge won't have much to bring back if they can't get their high Level Mermails into the graveyard; they can't even activate Mermail Abyssteus' effect to Special Summon itself, so they can't discard anything. Unless they're willing to let their hand size build up over several turns to discard Mermails in their end phase, they probably won't have anything to Soul Charge back that they can't set idly.
Majesty's Fiend is also one of the only monsters that can brutalize Geargiarmor without handing out a 1-for-1 in battle. Even if you're afraid it's a Fire Hand, Majesty's Fiend doesn't have any reason to worry about that. Outside of a strong backrow, there's nothing that keeps Majesty's Fiend from ripping apart fields with its bare hands in the battle phase completely unhindered.The Devil's Greatest Trick
Frog Monarchs are probably going to be the most common place this card pops up, even with the appeal of Return of the Monarchs, just because Treeborn Frog is such an advantageous Tribute Summon tool. If you weren't going to be using the Frog engine, how would you build a Monarch deck with a reliable stream of Tribute fodder? There are so many great facets of play that come with a card like Majesty's Fiend, from critically thinking the deck building process to managing resources to playing toward the goal of out-resourcing your opponent. It's an excellent card, and it's fair to say that anything that feasibly could run it likely will; make sure to keep an eye out for this one as the North American WCQ rolls by.