If you’ve never played IB, basically he gets a shout that taunts everything around him while boosting his durability and stamina. There are multiple ways you can use the ult, you can use it to attack while tanking the hits you take in return, you can turtle up and block for zero stamina, or you can kite enemies around while they are taunted and let your party finish them off. There are three possible talents at lvl 25 that modify the ult. The first increases the duration from 10 to 15 seconds, the second increases the taunt radius by 50%, the last one makes the taunt affect bosses as well as regular troops.
Something I recently discovered is that if you take the boss taunt talent it adds knockback to the ult that can stun and push bosses. This will ONLY apply if you take the boss taunt talent and the knockback is on par with mercenary and WHC shout.
Is this a feature or a bug?
On the one hand being able to stun bosses is awesome, you can even combine it with a conc potion to push them off cliffs just like any other class with knockback. On the other hand, it’s kind of counterproductive if the point is to taunt the boss. By the time the boss recovers from the knockback most of your 10 second ult duration will already be up. Plus being able to stun bosses at all makes this the meta pick out of the three lvl 25 talents in terms of utility.