Apparently Custennin might be more friendly with Merlin and Lady of the Lake than expected.
In the TCG, “Noble Knight Custennin” has been released with the following text:
• If this card is Special Summoned: You can Normal Summon 1 “Noble Knight” monster during your Main Phase this turn, in addition to your Normal Summon/Set (you can only gain this effect once per turn), also, you cannot Special Summon monsters from the Extra Deck for the rest of this turn, except “Noble Knight” monsters.
However, it has been noted that “Noble Knight Custennin” in the OCG has the following text:
• この特殊召喚に成功した場合に発動できる。このターン、自分は通常召喚に加えて1度だけ、自分メインフェイズにモンスター1体を召喚できる。この効果の発動後、ターン終了時まで自分は「聖騎士」モンスターしかEXデッキから特殊召喚できない。
Which would be, essentially:
• If this card is Special Summoned: You can activate this effect; you can Normal Summon 1 monster during your Main Phase this turn, in addition to your Normal Summon/Set (you can only gain this effect once per turn), also, you cannot Special Summon monsters from the Extra Deck for the rest of this turn, except “Noble Knight” monsters.
The difference is, for those not catching it, that “Noble Knight Custennin”, according to the OCG, provides a generic additional Normal Summon effect to the Link, Synchro or Xyz monster that uses it as Material, i.e. it is not restricted to just Normal Summoning “Noble Knight” monsters.
And that the Normal Summon is an effect you can optionally activate.
Which would make it, for the most basic example, very useful with “Merlin” and “Lady of the Lake”, two out of theme support monsters for “Noble Knight” monsters, who one would rather like to Normal Summon if given the opportunity.
It is currently unknown why there’s such a discrepancy between both territories.