Enraged

Summary
If a boss goes below half of it's maximum health, it will become enraged. What the enraged state does is cause the boss to become significantly more aggressive and therefore leaves less room for error for the player. Usually, bosses that become enraged make an attack go at a faster rate and extend it's length such as Thermite extending his inferno barrage, adds a brand new attack such as Demiglace straight-up charging at the player with her fists or simply just switches up the pattern a small amount such as Crysilla spawning more minions before resting on the pillar.