Deep North dungeonWinding Tunnels
40 per world · 32 to 48 rooms · 23 itemsA world seeds 40 of these under the Deep North, no two closer than 256 metres, and each one assembles 32 to 48 rooms out of a set of 32 pieces: 20 ordinary rooms and corridors, 2 entrances, 1 divider and 9 dead ends. That is what makes a tunnel long without making it complicated.
The reason to clear one is the mould set. 20 of them drop from the rubble down here, including 
Mould: Intricate Key, which no chest table in the game lists. Nothing marks a tunnel entrance on the map, so finding one is a matter of walking the Deep North.
Everything here rolls between one and three stars. The Elaking do not come from fixed spawn points: they pour out of Wardrobe Shafts, and a shaft keeps producing them, up to 100 in total and 5 at once, one attempt every 10 seconds once you are within 30 metres. Each spawn has a 10% chance to come out starred. The shaft itself is destructible with 300 health, which is the only way to turn one off.
Mould: Echo SpikePile of Rubble · 2.9% per rollMould: Intricate KeyWardrobe Shaft · 6.5% per roll
Mould: Lightning StrikePile of Rubble · 2.9% per roll
Mould: Nord AtgeirWardrobe Shaft · 3.2% per roll
Mould: Nord AxeWardrobe Shaft · 3.2% per roll
Mould: Nord BowWardrobe Shaft · 3.2% per roll
Mould: Nord BucklerWardrobe Shaft · 3.2% per roll
Mould: Nord CrossbowWardrobe Shaft · 3.2% per roll
Mould: Nord DaggerWardrobe Shaft · 3.2% per roll
Mould: Nord GreataxeWardrobe Shaft · 3.2% per roll
Mould: Nord GreatshieldWardrobe Shaft · 3.2% per roll
Mould: Nord GreatswordWardrobe Shaft · 3.2% per roll
Mould: Nord KnucklechainsWardrobe Shaft · 3.2% per roll
Mould: Nord MaceWardrobe Shaft · 3.2% per roll
Mould: Nord ShieldWardrobe Shaft · 3.2% per roll
Mould: Nord SledgeWardrobe Shaft · 3.2% per roll
Mould: Nord SpearWardrobe Shaft · 3.2% per roll
Mould: Nord SwordWardrobe Shaft · 3.2% per roll
Mould: Northern VengeancePile of Rubble · 2.9% per roll
Mould: Spirit CallerPile of Rubble · 2.9% per roll
Two breakables carry the mould table and they are not the same table. Both roll one to three times, and both hand over a guaranteed 
Timberwood on top of whatever the rolls give, but the Pile of Rubble has 23 entries against the Wardrobe Shaft's 19. The 4 staff moulds are the difference: they sit on the Pile of Rubble table only.
Roots growing through the tunnel walls are worth breaking as you pass. Each one is a coin flip for a single Timberwood, and 4 different root props are scattered through the set.
This is the long one of the two Deep North dungeons. The other, Mörkhalla, is four or five rooms against this one's thirty-plus, carries 19 of the same moulds, and holds the ice that starts a Jotun invasion. Everything the biome holds is on the Deep North page, and what 1.0 added covers the rest of the update.