Here's a Sunless Sea video showing me killing Mt. Nomad. I also explain several gameplay aspects including what equipment I had when I embarked on the hunt.

Timestamps:

00:00 Intro
1:03 The main weapon (the cannon) and the ammunition (Doomed Monster-Hunters) discussed
2:55 The Zubmarine submerging
3:41 Mt. Nomad location
4:10 I mistakenly fire a Doomed Monster-Hunter at a hostile sub
5:24 Megalops battle
5:40 Fragments explained
6:24 The importance of the correct mix of active officers discussed
7:44 The Lum of Blue Scintillak discussed
7:59 Permadeath, wills, improved lodgings in London, and heirlooms explained
9:16 Mt. Nomad battle
9:50 Looting Mt. Nomad
10:35 Mt. Nomad's Heart
11:19 Outro

[Obviously, SPOILERS AHEAD]


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How to obtain:

Icarus in Black (the cannon):

WARNING: This is a weapon that takes up the Forward slot of the ship. If your vessel doesn't have it, you can't equip it.

1. Go to the Iron Republic. It should be south of Fallen London, further down from the Cumean Canal.

2. Once there, the Story option "Fund a Tittering Artificer's Project" should be available. Fulfill that quest.

You will need:

1x Secret
7x Stygian Ivory
12x Devilbone Dice


Doomed Monster-Hunter (ammo for the cannon):

You can buy one from the following places:

Codex (Price: 1x Searing Enigma)
The Chelonate (Price: 1x Captivating Treasure)
Khan's Shadow (Price: 1x Element of Dawn (this is not recommended as the two areas above require something that can be aqcuired more easily than an Element of dawn))


Lump of Blue Scintillak (the fourth item in my Battle inventory bar; resets weapon cooldowns):

Refer to this page: https://sunlesssea.fandom.com/wiki/A_Lump_of_Blue_Scintillack#Obtaining