Arknights Wiki
Not to be confused with Terra, the world where the game takes place.
Make good use of special terrains and mechanisms on some maps.
—Loading screen tip

In Arknights, there are a number of terrains – unique tiles that bring advantages and disadvantages to friendlies and enemies when used correctly.

Terrain Feature
Protection Objective The objective where enemies will try to enter. Should an enemy enters a Protection Objective, the player will lose Life Points depending on the enemy in question.
Incursion Point Enemies will usually spawn into the map from an Incursion Point. Some operations feature Aerial Incursion Points from which flying units spawn.
Hole If a ground enemy (and only ground enemies) is somehow forced towards a Hole (which is done by shifting them), they will be instantly defeated.
Bush The friendly unit (and only friendly units) on a Bush becomes invisible.
Medical Rune The friendly unit (and only friendly units) on a Medical Rune will have their HP restored every second, which stacks additively with HP regeneration bestowed by skills and talents.
Defense Rune The friendly unit (and only friendly units) on a Defense Rune will have their DEF increased.
Anti-Air Rune The friendly unit on an Anti-Air Rune will have their ASPD reduced but deals more damage against aerial units.
Specialist Tactical Point The friendly unit on a Specialist Tactical Point will have their shift force increased, which is only relevant for those capable of shifting enemies.
Active Originium The unit on an Active Originium will receive an temporary effect that increases their ATK and ASPD but causes them to lose HP over time.
Heated Path The Heated Path periodically erupts, dealing Pure damage to units on it (the eruption interval and the damage dealt varies with the operation).
Poison Haze All deployed friendly units on the operation where the Poison Haze is present will lose HP over time.
Corrosive Ground The friendly unit (and only friendly units) on a Corrosive Ground will have their DEF halved.
Tunnel Enemy units who moved into a Tunnel Entrance will be moved into the Tunnel Exit of the same color after a delay that varies depending on the operation they are featured in.
Lava Crack Introduced in Heart of Surging Flame, the Lava Crack periodically sprays magma to the surrounding tiles, which deals Pure damage to friendly units (and only friendly units) including Roadblocks, which will be instantly destroyed.
Stump Introduced in Gavial the Great Chief Returns, the Stump is treated as a ranged tile, allowing friendly ranged units to be deployed on it, and appears in place of a Giant Mushrooms destroyed by Rhodes Island Temporary Employees. The Stump can be destroyed by Tiacauh Shredders and The Big Ugly Thing, permanently making it undeployable and instantly KOing friendly units deployed on the Stump.
Mark of Hui and Ming Introduced in Who is Real, the friendly unit deployed on a Mark of Hui and Ming will have their attribute set to either Hui or Ming depending on the Mark's color (black for Hui, white for Ming).
Mark of Dusk and Dawn Introduced in Who is Real, the enemy unit passing through Mark of Dusk and Dawn will have their attribute switched.
Sandstorm Introduced in Operation Originium Dust, friendlies caught in a Sandstorm will lose HP over time and have their redeployment cooldown increased if they are knocked out while inside it, while enemies will have their speed reduced. Dirt Mounds protect the tiles behind them from Sandstorms.
Gas Spray Only appearing in Defence Protocols, the friendly unit deployed on a Gas Spray will lose HP over time.
High Tide Introduced in Dossoles Holiday, enemies submerged in a High Tide will have their ASPD and speed reduced, and lose HP over time, while friendly units have their ASPD reduced and receives Corrosion Damage build-up periodically and when attacked.
Deep Water Zone Introduced in Dossoles Holiday, friendly units cannot be deployed on a Deep Water Zone unless with a Custom Floating Platform, and enemies will have their ASPD and speed reduced, and lose HP over time when they are forced to swim through it, or drown to their defeat in certain operations.
Visibility Introduced in Near Light, friendly units cannot be deployed on tiles without visibility and enemies inside them will become invisible. Visibility can be provided by deploying Operators close to tiles without visibility and through City Neons and Knight Crests.
Snowfall Introduced in Break the Ice, friendly and enemy units will intermittently be inflicted with cold while a Snowfall is active. Penetrating Cold Snowfalls also intermittently shift enemies.
Icy Surface Introduced in Break the Ice, friendly and enemy units on an Icy Surface will always be inflicted with cold and frozen enemies will also receive increased shift force. There are also Ice Streams which changes the direction enemies on it are to be shifted instead of increasing the shift force they receives.