Keystone Delta / Must-stop casts

Must-stop casts, straight from the game client

Since patch 12.0 the game carries a flag on every spell that says "this one is lethal if it is not stopped". It is the same flag that turns a cast bar red in the default UI, in Platynator, Plater and every other nameplate addon: none of them keep a list, they all ask the client. This page is that list, read out of the client and lined up against this season's dungeons.

Mythic+ Season 2

Each dungeon lists the flagged casts that actually happened in top-ranked runs, the mob that cast them, whether it is a hard cast or a channel, and how many times it came out per run. A channel has no wind-up, so the stop has to be a reaction. Spell names go to the Wowhead page through this site's proxy, so they open from geo-blocked countries too.

Altar of Fangs

Seen in 2 top-ranked runs (+20, +20).

Spell and who casts it	Type	Per run
Piercing HissPrimal Serpent	Cast	37
EvolveHigh Evolutionist	Channel	14
Toxic AtrophyThe Writhing Coil	Cast	6
Toxic AtrophyUncoiled Writhe	Cast	6

Den of Nalorakk

Seen in 2 top-ranked runs (+21, +20).

Spell and who casts it	Type	Per run
Frigid RoarFrigid Mauler	Cast	29
Healing BreezeEarthwhisper Tender	Cast	12
Arc LightningStormbound Mystic	Cast	7

Kings' Rest

Seen in 2 top-ranked runs (+20, +20).

Spell and who casts it	Type	Per run
Wretched DischargeHalf-Finished Mummy, Half-Finished Mummy	Cast	24
Poison NovaZanazal the Wise	Cast	5
Deathly RoarReban	Cast	3
Hex VolleyRisen Hexer	Cast	3
Unholy MendingSeneschal M'bara	Cast	2
Bind SoulQueen Wasi	Cast	1
HexPhantom Hex Priest	Cast	1

Murder Row

Seen in 2 top-ranked runs (+20, +20).

Spell and who casts it	Type	Per run
FelstormKystia Manaheart	Channel	20
SeductionSeductive Sayaad, Seductive Sayaad	Cast	10

Ruby Life Pools

Seen in 2 top-ranked runs (+20, +20).

Spell and who casts it	Type	Per run
Blaze VolleyBlazebound Firestorm	Cast	21
Flaming BarrageAshseer Flamelasher	Channel	21
Fiery BlastBlazebound Destroyer	Cast	19
Ice ShieldFlashfrost Chillweaver	Channel	8
Thunder BlastTempest Channeler	Cast	6
Frost OverloadMelidrussa Chillworn	Channel	2

Temple of Sethraliss

Seen in 2 top-ranked runs (+21, +20).

Spell and who casts it	Type	Per run
Flame ShockTwisted Hexxer	Cast	8
Addle MindFaithless Subjugator	Cast	7
Flame ShockTwisted Hexxer	Cast	3

The Blinding Vale

Seen in 2 top-ranked runs (+20, +20).

Spell and who casts it	Type	Per run
Light Bolt VolleyRadiant Spellsower	Cast	19
Disorienting ScreechLightfeather Petalwing	Cast	17

Voidscar Arena

Seen in 2 top-ranked runs (+20, +20).

Spell and who casts it	Type	Per run
Mad ShriekKilivore Screamer	Cast	13
Demoralizing ShoutDominated Brawler	Cast	12
Shadowbolt VolleyVoidtouched Magi	Cast	12
Violent SandAngry Krolusk	Cast	3

Flagged boss abilities elsewhere

Spells the Encounter Journal files under a boss in a raid or a dungeon that is not in this season's rotation.

Every other flagged enemy spell

Enemy spells the client flags that neither the top runs nor the Encounter Journal place anywhere: older dungeons, open world, delves, scenarios. Names lead to Wowhead if you want to know who casts them.

Player spells carrying the same flag

The flag is not enemies-only. Blizzard also marks big cooldowns and defensives on players, which is what makes them show up on enemy nameplates in PvP. Listed for completeness; the interrupt table ignores them.

How this was made

The client API is C_Spell.IsSpellImportant(spellID). A tiny addon asks it for every spell id, writes the hits to SavedVariables, and a script turns that into JSON. The flag does not exist in any datamined table and Warcraft Logs does not carry it, so this is the only way to read it. Dungeon and caster come from enemy cast events in the two top-ranked Warcraft Logs runs per dungeon, filtered to the flagged ids. A spell nobody's route pulls will be missing from a dungeon's table but still appears in the lists below it. Re-generated after each patch.