Buddy Synergy - If this hero is in a team with a certain other hero, then a trait will be unlocked or enables additional effects of a trait. (Sometimes more than one other hero is needed in the team.)
When Heroes are put on a team, they often buff each other. Some heroes need a specific other hero to do this. The team then unlocks a certain trait or adds more effects to a trait or special attack.
Dogs of War (Special Attack): 2 Melee Physical attacks on a random enemy. Rage adds additional ally attacks on random enemies twice. At 4 stacks of Rage, triggers Cry Havoc if on a team with Balog the Loud.
Mute (Trait): When on a team with Drakk the Warlord, chance to Silence enemies on Basic Attacks. Cry Havoc (Special Attack): Silencing Ranged Spirit attack on all enemies that Provokes the target. Triggers Dogs of War if on a team with Abigail the Brutal.
Like Father, Like Son (Trait): When on a team with Rogar Stonecrusher, Rogar will make a corresponding follow-up on the same target (basic attack followed by basic attack, 1st Ability followed by 1st Ability, etc.) after any attack made by this Hero.
Beastly Assault (Trait): When on a team with Solaris, chance to do an additional Basic attack on a random enemy at the end of each round. Twin Claws (Trait): When on a team with Jabber Clenchjaw, Jabber follows any attack made by Jibber with the same ability slot (similar to Like Father, Like Son).
Jack in the Box (Trait): When in a team with Cruel King Bramble all Goblins in the team have increased dodge chance and have a chance to apply paralyzed or dazed on hit. This hero can't be cloned. Jokes Aside (Trait): When on a team with Cruel King Bramble buffs on this Hero last twice as long.
Spirit Armor (Trait): After an allied Spirit dies health does not drop below 1 until the following turn. This effect can't be stolen, copied, or purged. Must have Harbinger, Undine, Moriko, and Vulcan as team members.
Valkyrie Valor (Trait): If there is a Legendary Fire Warrior ally on the team, Astrid becomes Fast and other Warrior and Honorbound allies start dungeons with an Aegis Shield.
Tangled Triad (Trait): If on a team with 2 or more allied Gorgons, self and Gorgon allies start dungeons with Invincibility for their first turn. Reptilian Alliance (Trait): When on a team with Grondar, this Hero becomes Fast.