Unlocking access to each craftsman in Enshrouded is the key to crafting new gears and creating new tools, which will allow you to make progress in the game and prepare yourself for the tougher fights ahead. As you upgrade the flame of your altar, you will be allowed to enter more dangerous Shroud zones.
Similar to all other craftsmen in Enshrouded, Farmer is also trapped inside one of the Ancient Vaults and you need to awaken her. Farmer's Vault is located north of Springsland and southwest of Revelwood Fast Travel Points. Unlocking Springland's Spire will highlight the location on your map.
The vault features a main door at the far end of the corridor, but it will only unlock after you activate three levers hidden inside the vault. Before you reach the main door, there is a branch of the corridor that turns left with a Grappling lock in front of it. Use the hook to reach the other side and follow the path. Jump over the pillars and use the ladder to reach the next room. At the far end of this room, you can spot the first lever, but you need to jump over electric bolts.
After activating the first lever, turn right and continue the path to the other room until you reach one of those flaming spheres. If you turn right at the end of the room, you will find yourself on the edge of the floor with two Grappling locks on the ceiling. You need to swing on both locks to reach the other side of the building, and as soon as you land, the second lever will be in front of you.
Continue the path to the right in this room and use the stairs and ladder to go up to the roof. Here, you need to head toward the balcony over the ruined wall, then turn right and move around the balcony until you reach an iron door. Open it and get inside. The third and final lever is visible at the far end of this room, but you need to jump over the spike trap first.
After activating the final lever, return to the main door, and you will find it open. Go ahead and awaken the Farmer, and then you can summon her to your base.