Typically for a Terminus cluster, the Tangeal has large amounts of strategic resources, such as platinum and eezo within its borders; these bolster the trade between Tangeal and the rest of the galaxy. The Expanse was dominated by three local superpowers and a few smaller states, and hosts many species, the humans being the most recent (but miniscule) newcomers to the cluster.
Several wars have been fought between the three larger nations over the strategic resources, most of them indecisive. Most recent conflict between the big three ended in destruction of the krogan-dominated Yuke Federation, leaving Velkans and Joseoans alive to distribute the cluster to their liking.
The big two remaining nations active in Tangeal are the Principality of Velka and the Federation of Joseo. They are about equal in size and strength, but Velka has historically been the more powerful faction, and continues to maintain this status through its ownership of the Future Corridor, safe passage via conventional FTL back to the Omega Nebula.
The smaller states in Tangeal used to be numerous and insignificant, most commonly consisting of a single planet or a moon or in the most extreme cases few settlements or space stations. Today they have been absorded by the Joseo and Velka in aftermath of Fourth Tangealian War. They served as buffer states and pawns of the big three during times of peace, but were frequently occupied when border wars occurred. One neutral nation of remark is Relay Point, its actual name lost to time immemorial, a system that used to host the other end of Albhon relay from Omega Nebula. It was a trading hub and all nations agreed it was best kept neutral for commerce during peace and negotiations in times of war. Relay Point has fallen into obscurity now because of the relays breaking up, and has descended into anarchy of pirates and privateers having lost its main source of income and support for organized law enforcement, servicing travelers coming through the relay.
Other lesser systems are the asari New Thessia and the human systems of Better World and Sawyer's Rock, latter only consisting of a few-hundred strong mining colony/stopover station. New Horizons was the most populous human system but it was annexed by Joseo after a border war erupted there between it and Velkans.
Once proud nation of strong warriors, the Federation of Yuke was blown apart in the Fourth Tangealian War to check the krogan's strength after the Genophage cure reached them. Velka-administered Dast II and Joseo-controlled Geert and Overlord's Fall (formerly Second Aralakh) are only systems with remaining habitable worlds and large populations of Yuke krogan and batarians. The rest, Yuke, Iro, Varkan and Death's Head were carpet-bombed with capital ship mass accelerators and dirty bombs by Joseo to make sure no life could take root there anymore.