While in the battle, you can tap and hold the Buff icon and read what it does.
Here's a list of heroes who can apply this effect:
- Emily (Leadership Ability)
- Victoria (Passive Ability)
- Eric Shieldbreaker (Ability 2)
- Niya (Ability 3)
- Solius (Leadership Ability and Ability 3)
- Hardorc (Ability 3)
- Zerra (Ability 1)
- Maar (Ability 3)
- Dieselrog (Ability 3)
- Garn (Passive Ability)
- Nightiel (Ability 3)
- Kiana (Ability 3)
- Telias (Ability 3)
- Teenty (Ability 3)
- Old Loor (Ability 3)
- Rin the Unseen (Ability 3)
- Master Duo (Ability 2)
- Kin Li (Ability 2)
- Hilda (Ability 2)
- Kang Xi (Ability 3)
- Lake (Ability 3)
- Lei Zi (Ability 1)
- Kulai (Ability 3)
- Boreas (Ability 3)
- Hera (Leadership Ability)
- Revol (Passive Ability)
- Yogi (Passive Ability)
- Bordwin (Ability 3)
- Hell Kitty (Ability 3)
- Nelly (Ability 3)
- Bar & Rel (Ability 3)
- Keb & Bab (Ability 3)
- Ace & Sin (Ability 3)
- Wizz & Ard (Ability 3)
- Slinger (Passive Ability)
- Puncherface (Ability 2)
- Shaiya (Ability 3)
- Buff (Ability 2 - one of the possible buffs)