If I, for example, am a hobgoblin warlord, and can raise an army of goblinoids, and I need to defeat, say, a Kraken, what can I reasonably do to make the soldiers of my army able to have any effect on the Kraken? The Kraken has immunity to "bludgeoning, piercing, and slashing from non-magical attacks", and does not mention any simple exceptions like silver or adamantium weapons. Are my 1800 waterbreathing hobgoblins, with underwater-capable weapons such as spears, totally necessarily impotent, and should just stay home? Or is there some spell, ceremony, material, magic substance, or other way to make them able to do at least half damage to it?
Fire, acid, poison, catapults, will all be problematic underwater. Thunder could be effective, if there's a reasonable way to equip hobgoblin soldiers with it. (Black powder is not available here, and hard to set off underwater anyway.) But I'm really trying to find a solution that could be applied to/with/by masses of humanoid soldiers who cannot themselves cast any spells, preferably that doesn't cost a ridiculous amount.
I can raise, equip (with normal weapons and armor), and transport (via longship) about 1800 goblinoids. Two spellcasters with Water Breathing cast as a ritual are enough to get them all breathing water for 8 hours or so. How can I make that force able to do something useful in this situation?
Best Answer
Craft Wands of Magic Missiles
If you're willing to sacrifice your soldiers, time and money, you might like to consider hiring or kidnapping craftspeople to Craft Magic Items. Specifically, Wands of Magic Missiles because it is an uncommon item which means that it is relatively cheap and easy to make, yet it has high reliable damage few creatures can resist. The cost of creating WOMM is much less than acquiring rare and obscure poisons and it is hundreds of times more effective than acid vials.
A Wand of Magic Missile has:
This means that each wand when fully discharged as a Level 7 spell does 9d4+9 force damage at a range of 120 ft. That averages out to 27 force damage per wand.
A Kraken with unrolled HP has 472 hit points, thus if you can craft 18 Wands of Magic Missiles, and each wand is discharged as a level 7 spell, you should be able to kill the Kraken from 120ft away in a single round 50% of the time.
If you fail, use your range to try and escape with all your wands and attempt again the next day. A Kraken can dash swim 120ft in a single turn so leave some goblinoids as bait to slow it down (and also to absorb hits from lightning storms) or strike from the shore.
Crafting WOMMs will require:
XgtE Version pg 128, 129
DMG Version pg 128, 129
You can also find another set of rules on crafting magic items in the DMG (pg 128, 129)
To craft Wands of Magic Missiles that way you'll need:
The creator of the wand must spend one spell slot of the spell's level on the item being created each day of the creation process.
As you can see, the DMG version is more expensive and requires more time but you do not have to risk your army.
The more wands the better!
If you craft 53 wands, you will be able to burst down a Kraken 100% of the time in a single round if every fully charged wand is completely discharged as a level 7 magic missile spell at a non-rolled HP Kraken that round.
In fact, an army with enough magic missile wands can burst down just about anything you come across in 5th edition!
Risk Mitigation
While discharging the WOMM at lower levels over several rounds will result in overall higher damage, keep in mind that this comes at great opportunity costs when fighting legendary creatures. A Kraken will be able to close into your ship in a single dash even if you had casted Magic Missiles from maximum range. Its legendary actions every round and Siege Monster trait means that it can very quickly destroy your ship! So burst it down in as little time as possible.