Elden Ring - Race to the DLC - 21 - Redmane Castle / Crucible Knight / Misbegotten Warrior

Make sure to do this before triggering the festival.

Before triggering the Radahn Festival (which occurs after progressing far enough in Ranni's questline or taking the Grand Lift of Dectus), the castle is populated with enemies and accessible doors. Key loot available during this phase includes the Red-Hot Whetblade, which can be found inside the building after bypassing the Iron Virgin.
The Armorer's Cookbook can be looted from corpses within the stable room, which is accessed after climbing a ladder from the exterior and defeating commoners.
A Smithing Stone is located in a chest in front of a knight on the rooftops, and another is found on a corpse near the stable.
Additional Smithing Stones can be found on the rooftops and in the stable room.
A Golden Rune is located on the upper section of the castle, accessible via a ladder from the west side.