| “ | Enemies will enter the tunnel from here and appear from where it leads to. | ” |
| —Tunnel Entry tooltip |
| “ | Enemies that have entered the tunnel will reappear from here. | ” |
| —Tunnel Exit tooltip |
Tunnel is a terrain feature in Arknights.
Overview[]
Tunnels are always found in pairs which consists of one Tunnel Entry and Tunnel Exit, linked by color. Ground enemies are able to move from a Tunnel Entry into the corresponding Tunnel Exit, essentially acting as a rapid method of transportation that could take the enemy across the map.
The enemy who enters the Tunnel Entrance are actually hidden from the map and stops for a period of time before being moved into the corresponding Tunnel Exit and continuing their path. While hidden, the enemy is subject to the following:
- Their sprite is considered to be right in the Entrance for the purpose of the enemy's positioning.
- Can neither be blocked nor targeted by attacks or abilities, but can neither attack nor use abilities as well.
- If the enemy is attacked right as they are hidden, the attack will still hit them.
- If the enemy becomes hidden while blocked, they will stop attacking the friendly unit blocking them and no longer being blocked.
- Before an update on July 9, 2020 in the CN server, if the enemy is shifted while next to the Tunnel Entrance they are heading, the enemy will become prematurely hidden.
- Before an update on July 9, 2020 in the CN server, if the distance between the Tunnel Entrance and Exit is far enough and the enemy is affected by Nightmare's
Night Phantom as they are moved from the Entrance to the Exit, the enemy will be damaged right as they reappears in the Exit. The update makes it so that the debuff (as well as that from Weedy's 
Liquid Nitrogen Cannon) do not deal damage if the enemy is moved greater than 4 tiles between a distance check (which takes 0.066 seconds).
Appearances[]
Tunnels are used in all Multivariate Cooperation operations as the means of connecting the Upper Level and Lower Level Test Areas for enemies.