Villagers are passive mobs that are best known for their many trades, which have been revamped in ROTN.
Villagers spawn primarily in villages, which come with guards, a Village Lord, watchtowers, Plague Doctor huts, and many of the pre-1.14 village structures. Due to the pre-1.14 mechanics, the majority of your villagers will be spawned in right at the start - besides making the old door houses or converting Zombie Villagers, it will be hard to generate new villagers to trade with.
Some villagers can be found outside of city limits wandering the countryside. Also known as Wandering Traders (not to be confused with the 1.14 caravans), these villagers spawn in and out of existence, each with a new set of trades. Their trades are random, to say the least, but can be worth leveling them up, especially for an early-game player. It is unknown if they can be bribed to stay by throwing an emerald block their way, though this worked in pre-3.0 ROTN.
Rarely, a pair of villagers with mules can be found far from town. Approaching these folk starts a sidequest where you have to escort them back to town. It is unknown whether they will trade before the sidequest is completed. This sidequest also comes with bandits that spawn: if the villagers die, the sidequest fails, but the mules are free for taking.
Like in Vanilla Minecraft, the strong suit of Villagers is in their trades. The currency of these folk is usually emeralds, but some variants take currencies like Sapphires or coins from the Nether instead. The GUI for trading is similar to the 1.14 style, as you can see and scroll through the entirety of their offerings. Due to being in pre-1.14, there are no workstations to refresh stock - instead, villagers from time to time will refuse to trade for a bit, followed by a new set of trades. This is more likely to happen if one or more of their trades have been used up. Additionally, many of the professions do not seem to level up, though confirmation of this would be appreciated.
ROTN has kept many of the old professions (with new trades), while also introducing new characters entirely.
- Fletcher: The base trades are selling arrows and bows for 1 & 2 emeralds, respectively.
- Miner: Can sell coal, coade cobblestone, iron & gold in block form, etc.
- Farmer: Buys & sells eggs, seeds, wheat, carrots, etc.
- Snow Villager: Buys blaze powder, snow, dragon bones; sells troll hide, frost dragon blood, etc.