The Poison card is unlocked from the Spell Valley (Arena 5). It is an area damage spell with a fairly wide radius and moderate damage. It creates a circular area in which troops and buildings are damaged slowly over time. It is a deep orange liquid in a thin oblong vial. A Poison card costs 4 Elixir to cast.
- Poison can be used effectively to damage both troops and buildings.
- It can be used to cripple the infamous spawner strategy, as it damages the troops that spawn from the buildings, along with the buildings themselves.
- The Poison will also affect a Witch and Night Witch in the same way as it affects spawning structures, damaging both the Witch and her summoned Skeletons. This can be useful in limiting their damage output while also leaving them at critical health.
- The Poison's damage is capable of fully defeating a Musketeer, Wizard, or Electro Wizard, but these troops tend to walk out of the radius before the spell's full damage can be dealt. To solve this, place any troop right next to the troop that is just about the walk out of the Poison's radius. This will distract them and make them stop moving, keeping them inside the radius.
- A Poison coupled with a Hog Rider is an effective way to deal heavy damage. The Poison will cripple all small units or swarms such as Minions and Minion Horde that the opponent may play to counter the Hog Rider. However, unlike the Fireball, the Poison can't defeat them instantly, so the Hog Rider will still get damaged.
- The Poison can be used to prevent players from placing small troops inside the radius. This can be useful if the player has a Prince or a P.E.K.K.A. in play.
- Guards or an Ice Golem paired with Poison can take out Three Musketeers.
- Poison can replace a Fireball if it is preferred to cripple anything in a larger radius. The only disadvantage is that the player won't be able to deal high damage to enemies immediately.
- Poison can be an effective counter to the Graveyard, sharing a similar duration. It covers most of its radius. However, a few Skeletons will still manage to damage the Arena Tower.
- Poison is also effective with the Graveyard since the Poison and Graveyard's duration are similar and Poison will defeat commonly used low health units such as the Goblins that are trying to defend against the Graveyard.
- Poison cannot one-shot Skeletons 2 levels above it, so players make sure their Poison is sufficiently upgraded.
- The Poison was added to the game on 29/2/16 with the March 2016 Update.
- On 23/3/16, a Balance Update increased the Poison's damage by 5%.
- On 3/5/16, the May 2016 Update changed the description of the Poison. The description prior to this update was "Covers the target area in a sticky toxin, damaging and slowing down troops and buildings. Remember: solvent abuse can kill!"
- On 20/10/16, a Balance Update removed the slowing capabilities of the Poison. This also changed the description. It was used to say: "Covers the target area in a sticky toxin, damaging and slowing down enemy troops and buildings. Yet somehow leaves the grass green and healthy. Go figure!"
- On 30/11/16, a Balance Update increased its damage by 10%.
- On 13/2/17, a Balance Update decreased its duration to 8 seconds (from 10 seconds), but increased its damage per second by 24%.
- On 12/6/17, a Balance Update allowed multiple Poisons to stack.
- On 12/12/17, a Balance Update decreased the Poison’s Crown Tower damage from 40% to 35% of the total damage.
- On 4/8/20, a Balance Update decreased the Poison’s Crown Tower damage from 35% to 30% of the full damage.
- The Poison uses the same deployment and sound animation in Clash of Clans.
- It is one of two direct damage spell cards that does not contain the phrase "Reduced damage to Crown Towers." in its description despite dealing reduced damage to Crown Towers, the other being The Log.
- Poison’s effect stays with troops for slightly after they leave the spell’s duration, seen when poisoning a Fast flying troop.
- In Clash of Clans, Poison slows and reduces hit speed of affected troops and does not affect buildings.