Dwarven Mythril Shield

Taken all the way down to base materials, one Dwarven Mythril Shield is 2 crafting steps deep and needs 3 intermediates — Dwarven Mythril Ingot ×2, Dwarven Mythril Nugget ×1 and Stonegold Ingot ×1 — which resolve to 6 distinct raw materials totalling 20 units, plus 41 crystals.

That bill outweighs 7,876 of the 13,602 recipes tracked here and 757 of the 1,441 Armorer ones, and 4,464 recipes nest deeper.

Only 14 of those crystals go into the final step; the other 27 are burned by the intermediates, so the real crystal cost is 14 Fire Crystal, 13 Wind Crystal, 7 Earth Crystal and 1 other kind.

The chain crosses three disciplines — Armorer to Lv 79, Blacksmith to Lv 78 and Goldsmith to Lv 78 — so no single class can finish it unaided.

All 6 raw materials are gathered, and one of them is time-gated: Gold Ore (9:00). That window comes round once per Eorzean day, every 70 real-world minutes.

Of the intermediates, Dwarven Mythril Ingot has the widest use: 168 recipes call for it, spanning seven of the eight crafting classes.