1: Valkyrie

Amongst the greatest warriors of the Northern Tribes, Valkyries are a race of large, female pegasi. They are fundamentally immortal, being in their prime for ages. This has allowed them to master pretty much every aspect of warfare and battle styles and makes them deadly foes to come across. Their reaction time is twicefold of a regular pegasus and their strength is the same. They are hailed as to saving the 'souls' of the best warriors and taking them to 'Valhalla', the home of the Northern gods. Valkyrie are born of either two ways: either being born naturally by a Valkyrie mother or a female pegasus was given the chance to become one.

2: Northern Tribesponies

Bred to weather the harsh climate and territory of the Northern Expanses, the Northern tribes are a hardy bunch. They are skilled in combat and masters of their frozen tundra terrain. They tend to be larger and stockier then your average pony, having a shaggier coat. This allows them to survive the harsh conditions and creatures of the area. Even unicorns, who aren't the hardiest of the three races, of the Northern tribes are noted to be exceptionally strong. Tribesponies of the North are always looking for a great fight, one that will land them in Valhalla. For this, they will eagerly jump into the fray and commanders can be hard pressed to get them to retreat.

3: Gullinbursti

Artificially created constructs, these golden hogs are extremely dangerous. They are magical machines, meaning they will not tire. They will not break ranks. They will do as programmed and smash their opponents into pieces. Their armor is hard to pierce and their 'manes' in fact spikes, which means if one was to try and jump them, you'd just end up impaling yourself.

4: Great Ravens

These large ravens act as scouts for the Northern Tribes. They are quick in both speed and wit and can outmaneuver most aeriel foes. They are also known as to land and peck out the eyes of enemies or stab them in crucial areas. Given that they are much larger then regular ravens, this can lead to some serious damage.

5: Berserker

Berserkers are amongst the few shaman types in Equestria. They are chosen as the strongest of the tribes and are sent into the wilderness to commune with the animal spirit that they will embody: namely, the bear. Naturally strong and tough, they can channel the creature's energy through them, giving them increased strength and ferocity. The more skilled Berserkers can even use their shamanistic magic to transform into large bears to tear apart enemy soldiers.

6: Imperial Sabre-Tyrant 

Known as one of the largest carnivores of all time, the Imperial Sabre-Tyrant is the largest tyrannosaurid to have existed. Native to the Frigid North, these large beasts are incredibly tough and ferocious. Just about everything that moves is nothing more then food to them. Even northern dragons are prey as their long, multiple sabre fangs can slice through the hard scales of dragons, something very few creatures can match. Their bite strength lends to their power, lending them one of the greatest bite forces on the planet. To add to their deadliness, they are known to be silent when hunting. You would never known one is be

Sweet Bersekers! also besides bears and other mammals is possible to be a shark or scorpion berserker?

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Possible, but these are the preferred animals of these tribes

thank you for your answer