This page contains the reasoning behind the KirriCorp League's original (now removed) errata on the card The Grave of Angels And Demons, shown below in its original form.

Name: The Grave of Angels and Demons
Type: Spell
Civilization: Light/Darkness
Cost: 4
Rules Text: [Shield trigger]. If there are two or more of a card with the same name in the battle zone, destroy all of them. Afterwards look at all mana zones, and if there are two or more copies of a card with the same name, destroy all of them.
Mana Number: 1
Set: Eternal Phoenix

The original reasons for removing this card from existence were gameplay related and not fundamentally mathematical. The card simply represented 'an effect that cannot be outplayed'. The closest approximations of this in regular play are Blizzard of Spears against decks that aim only for quick summons, or decks that use attrition and long term Disruption tactics, and Deklowaz, The Terminator, also against decks of this kind, provided they have no way to destroy Deklowaz.

Neither Deklowaz nor Blizzard of Spears offers a defensive measure against an extremely quick assault. A Blitz player may be utterly defeated by either card if the card appears before they complete their attack, but many other situations and cards shut their strategy down equally well. A Disruption player has little defense against Blizzard of Spears, but Deklowaz can be removed more easily.

In the end, the ability to shut down a particular decktype once the setup is completed, is not sufficient reason to errata a card in itself. The ineffectiveness of the card against other decktypes is taken into consideration, and the extreme effect allowed as a balance to the absolute ineffectiveness the card takes on when facing a different decktype, or when the opposing strategy is modified.

The forced movement counterstrategem induced by the card was analyzed. To overcome it, one needs to avoid placing copies of the same creature into mana, and similarly, onto the field. This can usually be easily accomplished even if one is unfortunate enough to draw multiple copies of the same card.

This counterstrategem creates an extremely strange 'dead card' effect in the hand of the player, especially regarding their mana zone. The inability to play two of a certain card to mana due to the risk of losing two mana cards purely by this choice, can be a heavy penalty for a card that is not actually being played. Easily destroying two opposing mana via spell effect is quite powerful. Doing it for only a cost of four, or possibly for free in the case of the card triggering, is close to devastation.

Fundamentally, the errata was applied to offer a certain level of protection to mono-decks, slightly, and to Disruption/Terminus styled decks that build large fields before attacking (see: Aqua Surfer, Locomotiver, Aqua Hulcus, Pala Olesis, Morning Guardian, Shadow Moon, Cursed Shade). It is fundamentally difficult for such decks to build a proper offense force in the face of this effect, since adding too large a varied number of creatures to their decks would result in a relatively large compromise to effectiveness.

The number of cards that can easily destroy two Fighter Dual Fang or Twin-Cannon Skyterror in a single cast, is a total of two (Invincible Abyss, Chains of Sacrifice). Both of these cards have at least slightly prohibitive levels of cost. However, The Grave has a prohibitive level of usefulness in terms of activation criteria.

At this time, the extreme detrimental effect of the existence of the card in its current form cannot be mathematically proven directly. It can only be considered proven if it is shown that, like Cranium Clamp (original) the effect occurs in such a way that a certain deck style has absolutely no reasonable way to avoid it. If this can be shown for either the majority of mono decks, or the majority of Disruption decks, errata will be considered again.

Note that in testing, the removal of Shield Trigger, though 'useful', was not considered sufficient to alter the negative scenarios created by the card, as it protects only Blitz and Assault, primarily. Disruption decks were still mostly devastated.

Result: Previous errata (ban) removed.

Name: The Grave of Angels and Demons
Type: Spell
Civilization: Light/Darkness
Cost: 4
Rules Text: [Shield trigger]. If there are two or more of a card with the same name in the battle zone, destroy all of them. Afterwards look at all mana zones, and if there are two or more copies of a card with the same name, destroy all of them.
Mana Number: 1
Set: Eternal Phoenix

In the event that the KC variant gains sufficient popularity for new players to pay attention to specific errata even if they represent a large change, then any necessary errata may be added to the Grave to make it fair. Feel free to test and suggest anything appropriate to Light/Darkness. However, before suggesting errata, one must first provide proof that one is necessary.