Celtic Howling Chain Blade is crafted with Blacksmithing in Mabinogi (weapon). This page lists everything needed to make it, checked against the game as it exists today. The interactive planner lives in the Blacksmith Companion.
How to get the manual
The manual is rank 3 and survives 30 uses; every crafting attempt spends one use.
Gilmore: general shop owner in Bangor, sells them at his counter (117,200 gold).
Materials
Expect about 8 attempts per finished item (13% average progress per attempt). Per-attempt materials are consumed on every attempt; finishing materials once per item.
Each attempt uses
2× Silver Ingot — refine from silver ore. Mine it in Barri Dungeon or north of Tory Ravine
8× Mythril Ingot — refine from mythril ore. Barri Mythril Mine/Advanced, or L-Rod ore deposits
3× Ruptured Black Metal — Rundal Basic dungeon reward
1× Infernal Blade Fragment — hard mode dungeon / hardmode-elite shadow mission reward
Finishing (once per item)
4× Tough String — weaving Thick Thread Balls
4× Incomplete Seal Emblem — Rundal Basic dungeon reward (also hard mode/Phantasm dungeons)
6× Runestone of Daring — Baltane Advanced Reward Box or large animal drops in Baltane missions