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 in the same way as it affects spawning structures, damaging both the Witch and her Skeletons.
- Since the Poison's damage is capable of killing a Musketeer, Wizard, or Electro Wizard but the troop tends to walk out of the radius before it dies, an Ice Golem paired with the Poison to keep the troop inside the radius works well.
- A Poison coupled with a Hog Rider is an effective way to deal damage. The Poison will cripple all small units such as Minions and Minion Horde that your opponent plays to counter the Hog Rider. However, unlike Fireball, Poison can't kill them instantly.
- Pairing Poison with the Bowler is a good idea since the Bowler's knockback can push medium-health swarms back into the poison radius.
- The Poison can be used to make your opponent not place small troops inside a radius. This can be useful if you have a Prince or a P.E.K.K.A. in play.
- Guards or an Ice Golem paired with Poison can take out Three Musketeers with ease. However, the opponent might deploy the Heal spell to nullify the Poison's effect and thus leaving the Three Musketeers alive.
- Poison can replace a Fireball if it is preferred to cripple anything in a big radius. The only disadvantage is that you won't be able to deal high damage to enemies in a short period of time.
- Poison can be an effective counter to the Graveyard, sharing a similar duration. It covers most of its radius. However, some Skeletons will still do damage to the Arena Tower.
- Poison is also effective with Graveyard since the Poison and Graveyard's duration are similar and Poison will kill low health units that are trying to defend against the Graveyard.
- 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.
- 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. However, in Clash Royale, it doesn’t.