The Monkin-doo and the Monkin-ban

Though seldom erupting into war the relationship between the Monkin-doo and the Monkin-ban is best seen as a conflict for these two closely related species (indeed some rate them as separate races of a single species) have a complex and tangled history with the circumstances of different times and locations meaning that sometimes one falls into a condition of near slavery to the other, sometimes a symbiotic relationships develops and may remain in places for extended periods (extending over centuries or even millenia) and sometimes the balance of power sways from one species to the other. 
It is notable that although there are occasional campaigns or crusades to free members of one species from the oppression of the other this is never known to have become a more widespread and general conflict. Both species seem to appreciate that they need the other and that only the most egregious examples justify the involvement of other communities. The arrival of the Morivian settlers in Tarusia has, perhaps, unbalanced this and may affect the relationship between the Monkin species.
One feature in this conflict that has been a constant surprise to human observers is how rarely an enslaved group attempts to leave for better circumstances. They do not welcome the slavery but both groups appear to value their territory more than their freedom. A minority, it is true, may leave or migrate, but they see themselves and are seen by others as having deserted their kin. Monkin found in human cities often fall into this category or are descended from them. The Monkin themselves see no puzzlement in this and will point out that the humans of Tarusia are all runaways from their own lands, even if like the Taru, they have been in Tarusia for millenia.

Monkin-doo Dominance

In areas where the geology is dominated by iron and other base metals the Monkin-doo tend to become more militant and domineering reducing the Monkin-ban to a state of serfdom producing food and other organic goods to support their masters.

Symbiosis

In areas where precious metals and gems are more common, the power is more evenly balanced (a sword of gold being really just an expensive and rather heavy club) and the relationship between the two tends be be more based on trade for the Monkin-ban have a love of finely wrought jewellery.

Monkin-ban Dominance

In areas where the land is poor in both base metals and precious, or perhaps where the seams have been mined out it is the Monkin-doo who find themselves reduced to the state of forced labour, usually in the form of quarrying or masonry.