Daine's cards

The Seal of Orichalcos
Field Spell Card
You must discard 1 card from your hand to activate this card. All face-up monster cards you control gain 500 ATK and are also treated as DARK monsters. This card cannot be targeted by card effects. This card is not destroyed if your opponent activates a Field Spell Card. You may summon monsters in your Spell and Trap Card Zone (they are still treated as Monster Cards). Monster in your Spell and Trap Card Zone cannot be selected as an attack target if their are any monsters in your Monster Card Zones. Once per turn you may move one monster between your Monster Card Zones and your Spell and Trap Card Zones. If this card leaves the field all monsters placed in your Spell and Trap Card Zones by this effect are destroyed. Pay 500 Life Points during each of your Standby Phases. If you do not, this card is destroyed.

Seems boring with the ATK boosting effect removed lol. Would it be possible to keep it if an activation and\or maintenance cost were added? Perhaps discard one card from your hand to activate it and pay 500 Life Points every Standby Phase to maintain it?

As for as the "back-row" effect. The closes I've seen is:
You may summon monsters in your Spell and Trap Card Zone (they are still treated as Monster Cards). Monster in your Spell and Trap Card Zone cannot be selected as an attack target if their are any monsters in your Monster Card Zones. Once per turn you may move one monster between your Monster Card Zones and your Spell and Trap Card Zones. If this card leaves the field all monsters placed in your Spell and Trap Card Zones by this effect are destroyed.

(Note that in the Japanese dub Rafael said that the seal expands the Monster Card Zones into the Magic and Trap Card Zones. The Spell and Trap Card Zone is the back -row. Which can be a negative effect if the Spell and Trap Card Zone got clogged and you can only move one monster out of it per turn.)

It's effect immunity could also be watered down, perhaps making it just unable to be targeted by card effects. That way it could still be taken out by mass Spell\Trap card destroyers like "Heavy Storm" but would at least be immune to the staple "Mystical Space Typhoon". The discard to negate an effect part could also be removed (it was never seen in the anime and was only ever used in special matches by Upper Deck during their "Duel the Master" matches).

Anyway, it would probably look something like this:

The Seal of Orichalcos
Field Spell Card
You must discard 1 card from your hand to activate this card. All face-up monster cards you control gain 500 ATK and are also treated as DARK monsters. This card cannot be targeted by card effects. This card is not destroyed if your opponent activates a Field Spell Card. You may summon monsters in your Spell and Trap Card Zone (they are still treated as Monster Cards). Monster in your Spell and Trap Card Zone cannot be selected as an attack target if their are any monsters in your Monster Card Zones. Once per turn you may move one monster between your Monster Card Zones and your Spell and Trap Card Zones. If this card leaves the field all monsters placed in your Spell and Trap Card Zones by this effect are destroyed. Pay 500 Life Points during each of your Standby Phases. If you do not, this card is destroyed.

And of course it would be a Limited card.

But anyway, speaking of new cards just I would like to remind you to check out Mahad's cards again since he might actually use some of them next story-line. Also Jade Eroe's cards since he will be a Dark Signer. Just spent time on this card as it might actually have a place in future story lines.

I fixed it, to MY own standard

Does it destroy monsters by its own effect or do you mean if you don't destroy monsters by some other means you have to pay the cost?

I have to destroy monsters by normal means. Or effect monsters, or effects.

Fayt, please take a look at this

Duke of demise
Card Attribute: Dark
Card Type: Fiend
Special Features: Effect
Attack Points: 2000
Defense Points: 1700
Effect/Description: This card cannot be Normal Summoned or Set. This card cannot be Special Summoned except by sending "Headless Knight", "The Earl of Demise" and "Polymerization" in your hand or on your side of the field to the Graveyard. This card cannot be destroyed by battle. During each of your Standby Phases, pay 500 Life Points or destroy this card.

Diabound kernel
Card Attribute: Dark
Card Type: Fiend
Special Features: Effect
Attack Points: 1800
Defense Points: 1200
Effect/Description: Once per turn, you can equip this card to a face-up monster your opponent controls, OR unequip it to Special Summon this card face-up on your field. The equipped monster loses ATK points equal to this card's original ATK. If the equipped monster is destroyed by battle, Special Summon this card face-up on your field. If this card destroys an opponent's monster by battle, it is also treated as that monster and gains its effect(s).