Some of the Nerf/Reduce/Extra damage perks are messed up, likely a confusion among more than one Bethesda developer, and it affects Alduin.
1. [00107E29] -
crReduceDamage05. Whoever named this perk originally intended it to reduce incoming damage, but it's been nerfing damage output by x0.5 since forever.
Primarily ghost and spirit type NPCs, such as Orchendor and the giant Mudcrab Spirit, use this perk, which Skyrim's design philosophy dictates ghosts take 50% less physical damage. Some of these ghost NPC records have both crReduceDamage05 and are also script-injected with GhostHalfDamagePerk [000D2058],
such as the Mudcrab Spirit and Potema's Remains. Others, such as the
Guardian Troll Spirit and Orchendor, lack the script-injected ghost perk but have the crReduceDamage05 perk.
To further support this, some characters, like dunHunterTroll or Orchendor, have both crReducedDamageTaken05 and crExtraDamage02 (modifies damage by x2). Both of those perks, in their current vanilla state, cancel each other out. For example, damage 10 * 2 = 20, 20 * 0.5 = 10.
Also, the "warped" and "broken" dwarven automatons in the Dawnguard DLC,
seen here, have crReduceDamage05, and I strongly suspect the intention was crNerfDamage05 (which I mention below) due to their supposed decrepit state.
Sorry if this is confusing lol. So some of these ghost NPCs need a ghost script + removal of the crReduceDamage05 perk, or just the perk if there's some weird design reason for why they lack the ghost perk.
I personally renamed the perk, and others like it, to crReduceDamageTakenX.
2. Alduin has crReduceDamage05. Since the game's release, people have complained how anemic Alduin is. Poor guy's damage has been cut in half compared to other dragons. However, dragons already have a perk in their race record that reduces damage from NPCs by 50%. By correcting the crReduceDamage05 perk and allowing Alduin to retain it, I guess that would make him take virtually no damage from NPCs (is it additive or multiplicative?) and 50% from the player. I wonder if their intention was for only the player, the Dragonborn, to be able to defeat Alduin in the final fight? After all, the game's lore states that Alduin is practically immortal/unkillable by mortals, and the only one who can stop him is a Dragonborn.
Only the Dragonborn can truly defeat Alduin because he is a divine entity, the "World-Eater," whose soul is anchored in Sovngarde, requiring the Dragonborn's unique ability to absorb dragon souls and use Dragonrend to make him vulnerable and force his true death.
3. [0010C041] -
crNerfDamage05, is erroneously named Extra Damage 1.5. For the most part this is a naming error and is typically used by low tier bandits. But it could help to properly rename it for modders. Also, this perk is literally identical to crReduceDamage05, which further led me to believe there is a bug here.

Attached Files:
Screenshot 2026-01-01 171945.png
Screenshot 2026-01-01 172252.png
Screenshot 2026-01-01 172614.png
Screenshot 2026-01-01 173056.png
Screenshot 2026-01-01 173312.png
Screenshot 2026-01-01 173331.png