Summoning Conditions Are Not Card Effects (Inherent Special Summons)

The Special Summoning procedure printed at the start of a Special-Summon-only monster's text — "Must be Special Summoned by …" / "Cannot be Normal Summoned. Must first be Special Summoned by …" — is a summoning condition, not an activated card effect. It does not start a Chain, it cannot be negated by effect-negation, and it is not an "effect that moves/Summons a card" for floodgates that only stop effects.

This is the inherent-Summon counterpart to Special Summon Negation (inherent Summons don't start a Chain) and the game-action principle in Unaffected vs. Cannot Be Targeted (a tribute that is part of a Summon is a game action, not an applied effect).

Necrovalley does not stop The Bystial Lubellion from Summoning itself out of the GY

Necrovalley — "… Cards in the Graveyard cannot be banished. Negate any card effect that would move a card in the Graveyard to a different place. …"

The Bystial Lubellion — "Cannot be Normal Summoned/Set. Must be Special Summoned (from your hand or GY) by Tributing 1 Level 6 or higher DARK Dragon monster. …"

Necrovalley is face-up. Can you Special Summon The Bystial Lubellion from your Graveyard by Tributing a DARK Dragon? — Answer: Yes. Necrovalley only negates card effects that would move a GY card. Lubellion's "Must be Special Summoned (from your hand or GY)" is its summoning condition — an inherent Special Summon you perform as a game action, not a card effect. There is nothing for Necrovalley to negate, so Lubellion leaves the GY and Summons normally.

General rule: a Special-Summon-only monster Summoning itself via its printed condition is never an "effect," so floodgates that only catch effects (Necrovalley's GY-move negation, "negate the effects of," etc.) don't touch it. Contrast a card whose activated effect Special Summons it from the GY — that is an effect, and Necrovalley / effect-negation would stop it.

The tribute in a summoning condition is a game action — Lava Golem, Interrupted Kaiju Slumber

When a summoning condition tributes monsters, that tribute is part of the inherent Summon (a game action), not "a Tribute by a card effect." So it can take monsters protected from being "Tributed by card effects," and it doesn't trigger effects keyed to being "Tributed by a card effect." Only explicit "cannot be Tributed" stops it (same logic as game action vs. applied effect).

Lava Golem — "Cannot be Normal Summoned/Set. Must first be Special Summoned (from your hand) to your opponent's field by Tributing 2 monsters they control. You cannot Normal Summon/Set the turn you Special Summon this card. …"

• You Special Summon Lava Golem to the opponent's field, Tributing 2 of their monsters as the summoning condition — a game action, so even a monster that "cannot be Tributed by card effects" can be taken; only a flat "cannot be Tributed" stops it.
• The "cannot Normal Summon/Set the turn you Special Summon this card" clause covers the whole turn — both before and after you Summon Lava Golem. Summoning it in Main Phase 1 still forbids a Normal Summon you might have wanted earlier or later that same turn.

Interrupted Kaiju Slumber — "Destroy as many monsters on the field as possible, then Special Summon in Attack Position, 2 'Kaiju' monsters with different names from your Deck (1 on each side) …"

Is Interrupted Kaiju Slumber legal if you already control a "Kaiju" monster? — Answer: Yes. It first destroys as many monsters as possible (including the Kaiju already out), then Special Summons 2 fresh Kaiju, one to each field. Already controlling a Kaiju does not block activation — the destruction clears the board first (see Resolve As Much As Possible). Handing a Kaiju to the opponent is likewise legal; that Summon is part of the procedure, not an effect-Summon they can stop with a Summon-negation aimed at "your" Summon.

Judge calls to watch for

• A Special-Summon-only monster Summoning itself via its printed "Must be Special Summoned by …" condition is an inherent Summon: it doesn't start a Chain, isn't negated by effect-negation, and isn't an "effect that moves a GY card" — so Necrovalley / GY-lock floodgates don't stop The Bystial Lubellion.
• A tribute that is part of a summoning condition (Lava Golem, Kaiju self-Summons) is a game action, not a "Tribute by card effect" — it can take "cannot be Tributed by card effects" monsters; only explicit "cannot be Tributed" blocks it.
• Lava Golem's "cannot Normal Summon/Set" applies to the entire turn, both before and after the Special Summon.
• Interrupted Kaiju Slumber is fine with a Kaiju already on the field — it destroys first, then Summons.

Sources

card texts via YGOPRODeck API (Necrovalley, The Bystial Lubellion, Lava Golem, Interrupted Kaiju Slumber). Bystial Lubellion under Necrovalley — the summoning conditions of Special-Summon-only monsters are not "effects that move a card in the GY," so Necrovalley does not negate them: Yugipedia "Card Rulings:Necrovalley" and YGOResources. Tribute as part of a summoning condition is a game action, not a Tribute by card effect: see 33_unaffected_not_cannot_target_equip_legal_target.md.