Because Zera Lore

[Bringerofcake]

Corrupted Slaughter

Normal Spell

Target 1 monster you control; Banish all other monsters that share its type, and if you do, skip all Battle Phases this turn.

 

Picture would be Arclord Zerato half contaminated with whatever made it its dark counterpart breaking stuff in SotS.

 

Fountain's Redemption

Continuous Trap

Special Summon this card as an Effect Monster (Fairy-type/Tuner/LIGHT/Level 1/ATK 0/DEF 0). It cannot be destroyed by battle. Once per turn, if this card would leave the field due to an opponent's monster card (by battle or by card effect): You can Set this card instead. If this card is used for a Synchro Summon, you must use only one other monster, and its Level is reduced by 1.

 

Picture would be Darklord Zerato wading in the Fountain in the Sky, looking remorseful or regretful somehow.

 

Umbralization

Continuous Spell

When a monster you control is destroyed by battle: Add, from your Deck to your hand, 1 DARK monster whose type, ATK and DEF are equal to the destroyed monster's, but with a different name. You can only use the effect of "Umbralization" once per turn.

 

Picture would be Arclord Zerato on its knees, with Darklord Zerato's sword at its throat.

 

 

Descent into Demonic Madness

Ritual Spell

(This card is always an "Archfiend" card)

This card is used to Ritual Summon any "Zera" Ritual Monster. You must also Tribute DARK monsters whose Level equals the Level of the Ritual monster you are attempting to Summon.

 

Picture is Mazera Deville watching in horror as one of his giant claws turns blue.

 

 

Ok, super headcanon time

 

Devil of Zera

DARK

Fiend/Xyz/Effect

R8/3000/3000

 

2 Level 8 DARK or "Zera" monsters

This card is unaffected by card effects. During either player's turn: you can detach 1 Xyz Material from this card to target 1 card on the field; banish that target. This effect of "Devil of Zera" can only be activated once per turn. If this card has a "Zera" monster(s) as an Xyz Material, it gains the following effects based on that monster's Attribute.

 

~DARK: When this card is Xyz Summoned: You can banish up to 2 cards in your opponent's hand or Graveyard, but this card cannot attack or activate other effects this turn.

~LIGHT: Xyz Materials attached to this card are banished instead of being sent to the Graveyard.

~EARTH: If this card is destroyed by battle; banish it, then Special Summon 1 "Warrior of Zera" from your hand, deck, or Graveyard.

 

more humanoid-looking Mazera DeVille with vaguely Mant-ish features.

 

Basically Darklord Zerato is umbralized (yes I stole that from Metaphization) and goes on a rampage (its effect) destroying most of the sanctuary of the sky. The only thing that remains is the Fountain. Zerato is purified by the fountain and becomes the lonely Angel of Zera. Meanwhile, within the darkest timeline the Mazera timeline, things pretty much turn out exactly the same, with Mazera becoming the Mant, and eventually forcibly combining with the First Lord of Horror to become the true king of Pandemonium. WHEE HEADCANON