Elden Ring Walkthrough - Part 3: Caelid

Part 2: Liurnia Hub Part 4: Altus Plateau

Recommended Stats Before Radahn: Level 50-70 | Vigor 35 | Weapon +12 to +15

1. Where to Start & Early Steps

Entering Caelid: The easiest way is simply walking east from Limgrave past the Smoldering Church. Alternatively, the trapped chest in Dragon-Burnt Ruins (Limgrave) teleports you to the Sellia Crystal Tunnel.
Scarlet Rot: The massive red swamp inflicts Scarlet Rot, a devastating poison. Stay on Torrent as much as possible, as he is immune to the swamp's effects while riding.
Dragonbarrow (North): The northern half of Caelid is scaled for much higher levels (Level 90+). Avoid fighting enemies here early on, but you can ride through to grab items.

Flame, Cleanse Me: An incredibly useful incantation found in the Fire Monk camp in eastern Liurnia. It requires only 12 Faith and cures Scarlet Rot. It is invaluable for Caelid.
Dectus Medallion (Right): Found in a chest at the top of Fort Faroth in Dragonbarrow. You need this to operate the Grand Lift of Dectus later. Run past the bats inside to grab it without fighting.
Millicent's Questline: Talk to Gowry in his shack south of Sellia. Defeat Commander O'Neil in the swamp to get the Unalloyed Gold Needle, and give it to Millicent in the Church of the Plague.

To fight the main boss, you must trigger the Radahn Festival at Redmane Castle (southeast Caelid).

Triggering the Festival: The festival starts when you rest at a Site of Grace in the Altus Plateau OR when you progress Ranni's questline to the point where you inform Blaidd about Radahn holding back the stars.
When the festival is active, the teleporter at the bridge outside Redmane Castle will take you straight to the courtyard, bypassing all the castle's normal defenses and enemies.
Speak to Jerren (the announcer) above the courtyard to begin the battle, then take the elevator down to the beach.

Weaknesses: Scarlet Rot and Bleed. Using Rot Breath (dragon incantation) makes this fight significantly easier.
The Gimmick - Summons: Unlike normal fights, you can summon a small army of NPCs by interacting with the gold signs on the battlefield. You can infinitely re-summon them when they die. Use them to distract him!
Phase 1: As you approach, he fires devastating gravity arrows. Dodge roll *through* them or use the weapons stuck in the ground as cover while making your way to the summon signs.
Phase 2 (The Meteor): At 50% health, he leaps into the sky. Look up and find the flaming meteor. Sprint away on Torrent in a perpendicular direction, as he will crash down and instantly kill anyone in the blast radius.