Spoilers ahead for the encounters in the third district, the route to the boss and the reward.
The Forest opens after the Construction Site. From the forest edge, the path runs along a trail and through a clearing full of roosters, then past the bank, lowlands and gorge into the thicket. The Great Dark Boar waits at the end. The surroundings change as you advance, and the barrier rules from the Construction Site no longer apply.
Following the route
Follow the main path and watch the name of the current section. You can explore the side pockets for finds or stick to the main route. The boss encounter doesn't require clearing every branch.
Early on you'll meet Create. Meeting him in the story and unlocking him for replay are separate events. More ways to play as him open after the castle. On return visits, the dialogue remembers your earlier meeting.
You'll find crates, individual crystals and shops along the way. Run resources help during the current attempt, while crystals add to the permanent balance. Weigh each detour against your remaining health. A little extra loot may be worth less than reaching the boss in good shape.
Reading the groups
Roosters are more common in the early sections. Slimes and golems appear later, followed by mixed groups. The movement that works against a small enemy rushing you differs from the approach to a heavy golem.
Several small enemies can block your retreat while a heavier one winds up. Look for space to move first and then choose where to use an ability. The position of the group will often matter more than the size of a particular enemy.
There is no district-wide kill requirement for the boss. Even so, running blind through unfamiliar groups can leave threats at your back and cut down your room to manoeuvre. Advance at a pace that leaves you an escape route.
The Great Dark Boar
The boss appears as you approach the final arena. Its main attacks are a straight charge after a run-up and a close-range tusk attack. Watch the warning and the direction it faces. Moving sideways out of the charge path usually works better than running directly ahead of it.
Check the edges of the arena before you move. If you're already boxed in, pressing an ability at the last moment may leave you nowhere to go.
Victory earns 40 crystals and opens the Castle of Legend. You can complete the district without clearing the side pockets or hunting down the remaining ordinary enemies.