Coming with an August 31 refresh and ladder reset of Hearthstone Battlegrounds is the keyword “Avenge.” Not to be confused with the Paladin secret “Avenge,” this new keyword will cause a minion to activate an effect after (X) friendly minions have died during combat. For example, the new card “Bird Buddy” has Avenge (1), meaning that after one friendly minion dies during combat, it will trigger its effect — which in this case, is giving all your Beasts on board +1/+1. Avenge cards can also trigger multiple times, meaning that proper positioning will be extremely important for squeezing out as much value as possible from this new effect.
Including Bird Buddy, nine new cards will include the keyword Avenge, ranging from Avenge (1) to Avenge (5). Avenge will offer support for Beasts, Elementals, Pirates, Murlocs, Demons, and Mechs, notably excluding Dragons. One Avenge card, Palescale Crocolisk, even shares its effect between Avenge and Deathrattle. Because of this, we can assume that in the future, Avenge will likely find itself interacting with more keywords. It is important to note that because this keyword is dependent on friendly minions dying, the lowest Tavern Tier Avenge card is Tavern Tier three.
This is almost certainly because any time before you could level up to Tavern Tier three, you likely don’t have enough minions on board for an Avenge effect to even trigger, meaning that generally speaking, Avenge cards are intended to carry you from the mid-game into the late game in a similar manner to Battlecry minions that provide permanent buffs.