When the player lands several attacks on a monster in quick succession, or deals a large amount of damage in a short time, the monster enters 'Rage Mode' where its attacks become more powerful, it moves more quickly, and becomes far more aggressive in general. Also, some monsters will take more damage from hits while in Rage Mode. Because of this fact, the veteran hunter can take advantage of Rage Mode and quickly end a fight.
Noticable visible effects of Rage Mode are the monster huffing coloured smoke from its mouth, colourations or markings appearing on the monster's body (ie 'tattoo' marks on Rathian and Rathalos' wings, Tigrex's arms and head turning red, Monoblos gains red marks on its head plate), or in the case of the Rajang, entire body metamorphosis. Also, all monsters roar before entering rage mode, so be wary if the monster seems to have some different feature then before after roaring.
Sometimes, when a monster is in Rage Mode, attacks and traps that usually work against it will cease to be effective. For example, When a Monoblos or Diablos is Enraged, Sonic Bombs will no longer cause it to become stuck in the ground while it's digging. Other monsters like the Yian Garuga can evade traps when Enraged.
Enraged monsters often introduce new attacks, such as an Enraged Basarios firing the 'laser' beams that its older self, Gravios, can fire. Another example would be Rathian's cluster fireball attack, an attack where Rathian takes several steps back, and then launches an explosive fireball that diverges into smaller fireballs at the point of impact.
Deviljho is a prime example of a rage mode monster. When entering rage mode, Deviljho will take a step forward and then roar as its body bulks up and it's back turns red, showing the monsters enourmous musculature structure. When it enters rage mode, it moves faster, does more damage, and is just devestatig. Not only that, but it also gains the ability to exhale a very dangerous blackish-red smoke that inflicts severe Dragonblight. This move in particular is extremely powerfull, so avoid it at all costs!
The best strategy against an Enraged monster is to guard (or if no guard is available, keep running and dodging), pick attacks, and don't get greedy. Powerful monsters, when Enraged, can quickly end a hunter's winning streak. Most monster can also be lured into traps more eisily during rage mode (if affected by them), which can give you time to either recover your health, get in more damage, or flee to a different area while the monster calms down.
Only 'Boss Monsters' have a Rage mode. Minion monsters, such as Velociprey, and the Dromes, such as Gendrome, do not have rage modes. This is most likely to represent the power or destructive capability of Boss Monsters.
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