Adult brains represent the second tier of hostile brains. They are tough, dangerous, and frequently spawn in the lower reaches of the underground.
Like all brains, they have shields that repel attacks. Adult brains can always protect against melee attacks, and each brain also has one random additional attack type that it can protect against. Therefore, fighting them one-on-one is easy enough, but when multiple brains are present a single weapon may not be capable of damaging them all at once.
Adult brains are sometimes summoned by brain lords, and players can spawn them with large spawners. They also occasionally spawn from culverts. In hell worlds, culverts always spawn adult brains (and nothing else). Like all mobs, adult brains can also spawn randomly in open areas underground.
Brains cannot move through open trapdoors. However, they can still shoot through them, so be careful.
Long periods of gunfire causes a brain to activate its shield. Instead, shoot in small bursts, or team up with another player and shoot two different kinds of attacks at once. Another tactic is to rapidly switch between two different kinds of weapons while shooting.
Each adult brain has two shields, a melee shield and a shield that enables it to better withstand one kind of gunfire. These shields are different colors, making it possible for the player to identify the type of gun that will be least effective. For example, if you're shooting a brain with an acid-based gun and it's showing a green-colored shield, you'll get faster results by switching to a different sort of gun. The shield colors and the weapon they correspond with are as follows:
- grey/black shield: melee weapons (pick, shovel, sledgehammer, tesla club, rapier, etc.)
- red shield: fire-based weapons (flamethrower, fire exploders, fire bombs)
- green shield: acid-based weapons
- yellow shield: energy-based weapons (including electric exploders)
- blue shield: frost-based weapons
Adult brains were the first brain introduced to Deepworld. They were originally more difficult to defeat, but once more elder varieties of brains were added, their difficulty level was decreased.
Over time, players discovered that placing earth blocks on the bottom half of any brain would immobilize it and prevent it from shooting, thus making it very easy to kill. Eventually brain mechanics were tweaked so that brains could "shovel" through blocks placed on top of them.
Adult brains represent the juvenile age level of the brain continuum. They are the smallest brain to appear outside of Brain worlds, as their tiny baby brethren are considered too weak to venture out and terrorize the populace. In order to progress to ever-more mature status, adult brains must complete a number of missions against human survivors, which is why they are frequently seen in combat.