The Pech is both an introductory research option found under the Basic Information tab, and a neutral mob.
Pech are small creatures who can be found in magical biomes (Eerie and Magical Forests). These creatures have 15 hearts, or 30 points of health, and 1 point of armor. They are similar in nature to Zombie Pigmen, neutral mobs who will attack when provoked, alerting other nearby Pech. They attack for between .5 and 1 heart, 1 to 2 points, of damage with a bow, or can also attack by hand for 2 hearts, 4 points, of damage.
A unique property of the Pech is the ability to pick up items off the ground, of which they will do with almost every item dropped, and their ability to trade with the player. While they will pick up anything, trading is dependent on items with the Desiderium Aspect, like items as follow: sugar, gold coins, gold swords, bottles of Desiderium Essentia, emeralds, and treasure bags. Pech can be "befriended" for a short period of time, up to 5 trades, by dropping enough items of any kind, and can then be traded with until the "friendship" must be renewed. As more expensive, in the sense of Desiderium, items result in this "friendship" more quickly, and items Pech pick up can be traded back to the player, it is suggested not to use cheaper, more abundant materials to initiate the ability to trade. This trade is random, so the return can be better or worse, with items containing more Desiderium generally netting better results. Although there are multiple variants of Pech, the most common is the Pech Forager.
There is a bug where Pech trading can rarely crash the game. It should also be noted that friendly Pech are prime targets for guard Golems and stray lightening bolts. They can also despawn unless named.