The previously Forbidden cards aren’t the only ones with updated effects in 20AP.
Up to this point in the OCG, Necrovalley has worked in essentially the same way as the TCG version is currently written (although players familiar with its history might remember that it took more than a few tries for the TCG to get it right). As a reminder:
All “Gravekeeper’s” monsters gain 500 ATK and DEF. Cards in either player’s Graveyard cannot be banished. Negate any card effect that would move a card in the Graveyard, other than itself, to a different place.
However, in the new 20th Anniversary Pack printing, the card states something closer to “negate any card effect that applies to cards in the Graveyard”, which is effectively omitting the “other than itself” part. (The definition of “applies to cards in the Graveyard” is still the same; it means moving cards to a different place.)
①：フィールドの「墓守」モンスターの攻撃力・守備力は５００アップする。②：このカードがフィールドゾー ンに存在する限り、お互いに墓地のカードを除外できず、墓地のカードへ及ぶ効果は無効化され、適用されない 。
The result is that Necrovalley becomes a much stronger floodgate, because it will negate effects of cards that do take themselves out of the Graveyard that it previously allowed, such as Paleozoics’ Graveyard effects, Glow-Up Bulb, Sinister Serpent, Grapha, Dragon Lord of Dark World, Metalfoes Fusion’s second effect, Madolche monsters’ common effects, and so forth. More in-depth individual rulings will follow when I get around to posting the 20AP rulings.
It is currently unknown if and when this change will occur in the TCG, as with the other updated cards in 20AP.