Once there was a race of insects known as the Sabits, humble travelers who lived in peace with their neighbors, fighting only when necessary. However, another species of insect, the Formians, became intent on wiping out the peaceful race, eradicating them until they had been wiped out...

Or so it seemed. Two populations survived. When the Sabits were being wiped out, a small group managed to escape the destruction. these survivors, all breeding females and kings, split into four factions. The breeding females and the kings who managed to survive split into four groups:One focused on becoming smaller, mainly focusing on being really quick flyers.One became stronger, modifying part of their mandible structure into a single arm and re-building a partial "hive mind"One focused on becoming even stronger, believing brute strength combined with speed was the best.And finally, one believed brains was the answer. Ironically, this group was mostly females.The four groups still interbred, to keep the gene pool fresh, and eventually re-merged into a single species: the Tirbana. in Sabit, it means "New Dawn"

The other population was found by the Skeksis, who began breeding them into a subservient race of guards.

the Garthim are large insects, divided into two castes: the Queen, and a worker/warrior caste. They WERE little more than mindless beasts due to their old masters monitoring their breeding and culling any who showed too much brains. However, the Skeksis died out long ago, shortly after the Founding of Equestria. When the Skeksis died out, the Garthim had no masters, and no one to cull the smarter individuals...

they were found by the Tirbana, who began to immediately debate on whether they should take a hand, and guide their fallen brothers back to the Light of Intelligence.

While Tirbana are smart, Garthim rely on numbers, strength, and armor, and an ability to emit a fog from between their plates. any animosity they felt towards Formians is long forgotten, as the current Garthim are too stupid to remember it.

their weaknesses include their general stupidity, the fact that they are not fast or particularly agile (they don't go around objects, they try to move them if there's not enough space to go around), and low-pitched noises, which cause them to become docile.

I feel a bit sorry for these guys. I mean, they can't help it, can they?
The Skeksis were just arrogant douche-birds that disregard any knowledge that doesn't suit them but the Garthim just seem to be generally unintelligent.

5958807 they're slowly getting better