In this wiki, the components behind the combat mechanics of gym defenders will be explained. When it comes to gym defenders, other factors can be observed such as CP decay, berry feeding, coin rewards, etc.
However, the focus here will primarily be on the combat mechanics, therefore please refer to the appropriate wikis if what you see is regarding the previously mentioned topics.
Gym Defenders are Pokémon that another Trainer left in the gym to defend it. They are controlled by an AI (Artificial Intelligence).
Gym defenders do not dodge, making it easier to ensure that your Attacker has the maximum damage output possible.
A Gym Defender is not able to switch Pokémon throughout the fight. They will go one by one in the chronological order in which they have been placed in the gym.
3. Stamina (HP)
Gym Defenders have their stamina doubled. For instance, if you place a Machamp with 154 HP in a Gym, when defending the gym, Machamp will have twice this amount of HP – 308.
As a result, Gym Defenders can tank more damage, but we will see that they also deal less damage.
4. Energy Generation
Gym Defenders generate energy, which is used to charge their charge moves. Based on their HP loss, more specifically, they generate 1 energy per 2 HP loss.
5. Fast Move
A Gym Defender’s first attack will occur at 98.4 seconds on the combat timer, and will have a duration of 1.5~2.5 seconds. Every subsequent fast moves will have the same duration.
Tip: An attacker’s first attack can occur at 99.3 seconds on the combat timer. This implies that depending on your Attacker’s fast move, you are most likely to be able to throw one fast move before having to dodge the Defender’s initial attack.
6. Charge Move
A Gym Defender’s charge move will have the same duration as its fast move, therefore 1.5~2.5 seconds.
The most popular theory related to the usage of a Gym Defender’s charge move goes as follows:
There is 50% chance that a Gym Defender will release its charge move once it has gained sufficient energy.
This means that once the Defender has gained 100 energy, the AI would have 50% chance of releasing its charge move. Should it fail to do so, it would release a fast move. On its attack, there would still be 50% chance of releasing it charge move, and so on. Should this theory found itself to be true, may the odds be in your favor trainers.
7. Weather Factor
As we are publishing this wiki, we are still looking for evidence pointing towards the fact that in-game weather effectively boosts a Gym Defender’s attacks (Refer to Weather and Moves’ Wiki for more information on how the in-game weather affects moves); or the opposite, which is that the in-game weather does not affect a Gym Defender’s attacks.
Unlike the Attacker, who will see in the bottom right corner of the screen, at the beginning of the combat a notification indicating that the Attacker’s attack(s) are boosted by the in-game weather (see picture below); there doesn’t seem to be any indication of the sort for the Defender.