So I did a brief analysis of the attack and creature types in the pet system. There are a total of 10 types, each with a special passive effect:
- Aquatic - Harmful damage over time effects are reduced by 25% on Aquatic Pets.
- Beast - Beasts deal 25% extra damage below half health.
- Critter - Critters break out of crowd control effects more quickly.
- Dragonkin - Dragons deal 50% additional damage on the next round after bringing a target’s health below 25%.
- Elemental - Elementals ignore all weather effects.
- Flying - Flying creatures gain 50% extra speed while above 50% health.
- Humanoid - Humanoids recover 4% of their maximum health if they dealt damage this round.
- Magic - Magic pets cannot be dealt more than 50% of their maximum health in one attack.
- Mechanical - Comes back to life once per battle, returning to 20% health.
- Undead - Undead pets return to life immortal for one round when killed.
Each pet is one of these types. Each pet’s abilities is also one of these types (all pets have 6 abilities (not all of which are attacks), unlocked at levels 0, 2, 4, 10, 15, and 20), though pet abilities are not necessarily the same type as the pet itself (though they often are). Lastly, each type has two other types associated with it, one that they are weak against (they take 50% more damage) and another that they are strong against (take 33% less damage).
Strengths and Weaknesses don’t follow the same progression. The weakness progression is as follows. For each type entry, it is weak against the type directly above it (thus, for example, Beasts take 50% additional damage from Mechanical attacks, while Critters take 50% additional from Beast attacks).
The strength scale operates the same way. For each type entry, it is strong against the type directly above it (so for example, Critters take 33% less damage from Elemental attacks, while Humanoids take 33% less from Critter attacks).
One thing to note here is the relationship between Elemental and Mechanical. This is the only matchup where one type (Elemental) is strong against another type (Mechanical), which is also weak against the first type. In addition, Mechanical pets have almost exclusively Mechanical abilities (though many also have a single Beast ability), and Elementals tend to have mostly Elemental abilities as well, meaning that if an Elemental pet matches up against a Mechanical pet, the Mechanical has almost no chance, as they are simultaneously taking 50% additional damage and dealing 33% less. This makes Elementals vs. Mechanicals the one true hardcounter in the pet battle system, and also could conceivably make mechanical pets somewhat underpowered (particularly given how many elemental pets exist).
This sets up an important idea when choosing a pet: find pets which have abilities which are strong against the type that pet is strong against. For example, if you were looking for a dragonkin pet, you’d want to try to find one with abilities strong against flying creatures (which innately deal less damage to dragonkin). Flying creatures are weak to magic damage, so you’d want to find a dragonkin with at least one damaging magic ability, if possible.
By the same token, finding creatures with abilities that are strong against the type that creature is weak against can also be a good idea, just in case you’re forced to fight in such a situation. For example, undead creatures are innately weak against critters. Finding an undead with at least one damaging beast ability can offset that weakness, essentially canceling out the additional damage you’re taking by dealing additional damage right back through the opponent’s weakness.
Lastly, finding pets with abilities that are strong against the type they deal less damage to can be beneficial. For example, critters innately deal less damage to humanoids. Having a critter with access to an undead attack (which deals additional damage to humanoids) can offset that weakness in case the opponent decides to try to tank your creature.
Lastly, here’s a handy chart of the strengths and weaknesses. Blue represents a strength (the attacker is dealing 33% less damage to the defender), while Red represents a weakness (the attacker is deal 50% more damage to the defender). Remember, while the pet’s type determines the defending type, the type of theability being used (not the type of the attacking creature) determines the attacking type, and therefore the type matchup on the chart.