The Trials of the Ancients is a feature featured on the zombies map Zetsubou No Shima. These trials are challenges that will reward the player upon their completion. There are sixteen different challenges, but each player has to complete three of them in each game.
The three rewards are:
- Top trial gives the player an Empty Perk Bottle.
- Middle trial gives the player either a Dingo, SVG-100 or 205 Brecci. Letting the weapon drop back into the altar can allow the player to reopen the altar until they get the gun they prefer.
- Bottom trial gives the player a Max Ammo.
- Eat a fruit grown by a plant.
- Kill eight spiders with spores.
- Kill three zombies as they are mutating.
- Get thirty kills with the Propeller Trap.
- Shoot the heads off of five mutated zombies.
Upon completing all challenges and receiving all the rewards, lightning will occasionally strike the ritual area. If the player holds out a shield while being struck by the lighting, they will be able to electrify their shield. On co-op, all players must complete their respective challenges and receive their rewards before anyone can acquire the electric shield. Acquiring the electric shield is required to get the Seeds of Doubt and Assault with Battery achievements/trophies, while it is also required to upgrade the KT-4 and get the Spider Bait.
- Eat a fruit grown from a plant: In order to do this,the player needs a bucket and a seed. What the player has to do is water the seed for three consecutive rounds using different water each time (purple, blue, green). After doing so, the player will be able to eat the fruit and complete the challenge.
- Obtain a power-up from a plant: To complete this challenge, the player needs a seed and a bucket with blue water. All the player has to do is plant the seed and water it for three rounds with blue water. Then, a purple pod will grow and after the player harvests it, they have high chances of getting a power-up. Note that the Bonus Points power-up from single pods does not count for the challenge.
- Kill fifteen zombies attracted to a plant: For this challenge, the player has to water a planted seed three times using purple water. After that, a plant that attracts and kills zombies will grow. To complete the challenge, the player simply has to kill the zombies that are attracted to the plant, before the plant kills them.
- Kill a Thrasher before it becomes enraged: This challenge is a bit difficult. The best way to complete it is to use the Skull of Nan Sapwe in order to kill the Thrasher quickly. The player can also use weapons with high damage (such as the Marshal 16) on early rounds while the Thrasher is spawning from the ground. If the player manages to kill the Thrasher before it becomes enraged and starts running, the player will successfully complete the challenge.
- Kill three zombies as they are mutating: In order to complete this, the player has to kill a zombie while it is becoming a Thrasher three times, but before it is pulled into the ground. A zombie will actually become a Thrasher if it gets infected by one of the spores. This means that the player has to be ready to kill a zombie when it gets near a spore, since there are high chances for the zombie to become a Thrasher. The player will find a zombie as it is mutating when opening the bunker, but the player will have to be a little bit quick in order to kill it before it becomes a Thrasher.
- Use a spore to regain air underwater: This is an easy one. There are some underwater areas in the map, such as the one in the power room and the one next to the Mule Kick. In these areas, there are some spores. What the player needs to do is get near them, destroy them, and enter the cloud which was left by the spore. Instead of coughing, the player will regain air and that's how the player completes the challenge.
- Kill twenty zombies while underwater: To complete this, the player has to kill zombies in underwater areas of the map. Some of these areas are mentioned above. After the player has killed twenty zombies while being under the surface of the water, the player will complete the challenge. Zombies killed while underwater in the process to turn on the power will count.
- Shoot the heads off of five mutated zombies: For this challenge, the player has to wait until Thrashers spawn in. Once a Thrasher comes, the player has to aim for its head, instead of the spores. This will eventually cause the Thrasher's head to disappear and once the player notices that the head is missing, they are ready to move on and repeat this four more times.
- Kill eight spiders with spores: This challenge is an easy one. The player has to wait until spiders come in. Once spiders have come, the player has to lead them inside spore clouds. When the spiders get inside these clouds, they will die. Kill eight spiders in this way and the player will complete the challenge.
- Destroy five webs with explosives: To complete this challenge, the player has to find five webs and destroy them with explosives (Ray Gun shots count). The easiest way to complete it is to use frag grenades. The player can find some of these webs on GobbleGum machines and Perk-a-Cola machines. Spiders will also put webs in pathways in order to block the player. Destroying these webs with explosives will count too.
- Get thrity kills with the propeller trap: Lead some zombies to the propeller trap, activate it and wait until thirty zombies are killed. The trap is found in an area between Lab A and the spawning area.
- Get twenty kills with the fan trap: Much like with the propeller trap, the player has to activate the trap and wait until twenty zombies are killed. The trap is located on the staircase leading to the Flak 88 area.
- Kill ten spore-infected zombies with headshots: In order to complete this challenge, the player will need spore-infected zombies. The player will understand whether a zombie is infected or not, since the infected ones have an orange cloud around them. The challenge will be completed when ten of these zombies are killed with headshots. Also, killing a zombie while Insta-Kill is active will count even if the player doesn't shoot its head.
- Shoot five spores: This might be the easiest one to complete. All the player needs to do is destroy five spores. It doesn't matter if the player knifes the spore instead of shooting it or if the player destroys the spore while it is too small.
- Water five plants: For this challenge, a bucket and seeds are required. What the player has to do is water plants. After the player has watered plants five times, the challenge will be completed.
- Water the same plant three times: Unlike the previous challenge, the player has to water the same plant three times. To do so, the player needs to water a plant, wait for the next round, water the plant again, wait for the next round, and water it again. After doing so, the challenge will be completed.