Eidos the Underworld Monarch – #DUAD-EN017
If this card is Normal or Special Summoned: You can add 1 “Monarch” Spell/Trap or 1 monster with 2800 ATK/1000 DEF from your Deck or GY to your hand. You can declare 1 Attribute; make 1 face-up monster on the field become that Attribute. If you Tribute Summon a monster with 2400 or more ATK and 1000 DEF, while this card is in your GY: You can add this card to your hand or Special Summon it. You can only use each effect of “Eidos the Underworld Monarch” once per turn.
Date Reviewed: November 7th, 2025
Rating: 4.13
Ratings are based on a 1 to 5 scale. 1 is awful. 3 is average. 5 is excellent.
Reviews Below:
Crunch$G
The week ends off with Eidos stepping up from his Squire status to become Eidos the Underworld Monarch.
Eidos is a Level 6 DARK Spellcaster with 2400 ATK and 1000 DEF. Stats are good, DARK is great, and being a Spellcaster makes Magicians’ Souls a bit more viable in Monarchs. Upon being Normal or Special Summoned, you can add any Monarch Spell/Trap or any monster with 2800 ATK and 1000 DEF from your Deck to your hand. Instant searcher for your backrow or Mega Monarchs is great to access, even if you likely have to Tribute Summon it to do so first off, or it makes for another good target to summon from the Deck with Ehther the Heavenly Monarch. You can declare an Attribute to make a face-up monster on the field into that Attribute, mostly to make the Mega Monarchs get their full power effects by tributing a monster with the corresponding Attribute. Finally, if this card is in your graveyard when you Tribute Summon a monster, you can either add it back to your hand or Special Summon it, which will likely be the latter to trigger the first effect again or at the very least put a big body back on the board. HOPT on all three effects. Eidos is great for consistency, something Monarchs have struggled with in the past, while also making Mega Monarchs more viable and recovering itself to use its first effect again potentially. For sure a smaller Monarch you should be playing.
As for Genesys, it’s still a powerful card to search for your Domain that you’ll have to play less copies of due to the point requirements, otherwise it searches your other standard good Monarch backrow.
Advanced Rating: 4.25/5
Genesys Rating: 4.25/5
Art: 4.5/5 Eidos is hungry for power now.
Mighty
Vee
Eidos finally achieves its dream as a new Monarch monster to end the week, Eidos the Underworld Monarch, a level 6 DARK Spellcaster monster and weirdly enough another DARK Monarch, not that I mind! The usual Monarch searchers will get to it, though in my experience you’ll want to summon it with Ehther the Heavenly Monarch since it’s the only Monarch that actually triggers on Special Summon and does not actually need to be Tribute Summoned. Unsurprisingly, Eidos comes with the typical Monarch stats of 2400 attack and 1000 defense– not great, but mandatory so that your combos can actually function.
Eidos has, what else, 3 hard once per turn effects, all of them being combo utility so it’s not really a boss monster. The first triggers on Normal or Special Summon, simply searching either a Monarch Spell or Trap or any monster with 2800 attack and 1000 defense, or recycle one of those cards from your Graveyard. The usual cards you’ll want to search are Domain of the True Monarchs and The Monarchs Erupt, since they’re half the reason you play Monarch, though of course if something else is more important, get it! The monster is obviously going to be one of the Mega Monarchs if you so choose, so this is also a good opportunity to grab Erebus the Underworld Monarch if you need it but don’t have it yet. Eidos’s second effect will simply let you make 1 monster on the field become any attribute. This is almost useless by itself, so it’s meant to combo with the Graveyard effect of The Monarchs Masterplan to guarantee the attribute of mini Monarch you want. It’s a lot of moving parts to set up, so I wouldn’t rely on it outside of emergencies. Eidos’s final effect takes a page from Erebus’s book, triggering if you Tribute Summon a monster with 2400 or more attack and 1000 defense while it’s in your Graveyard. It’ll let you either Special Summon Eidos, or recycle it back to your hand. You’ll almost never recycle it outside of niche gamestates where you need a Monarch to reveal for Tenacity of the Monarchs or if your opponent has effects that punish you if you have too many monsters. You’ll mostly want to Special Summon it directly; Monarch will never say no to Tribute fodder, especially self-recycling Tribute fodder! Eidos does a lot for the deck, mostly by getting to your backrow– the floodgates, or Monarchic Perfection in Genesys. Of course, in true Monarch fashion, it is also a horrible brick! Tragically, you’ll still want to run it at 3, since the Graveyard effect is too good to pass up if you get the chance to discard it or summon it with a Squire.
+Great combo piece that can access backrow more easily
+Enables powerful boardbreaking with The Monarchs Masterplan
-Attribute change is useless without Masterplan
-Utterly terrible as a brick if you don’t open a good hand
Advanced: 4/5
Genesys: 4/5
Art: 3.5/5 A bit plain, I guess Eidos isn’t the most creative guy of the bunch.
King of
Lullaby
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