What happend to the Seleucid empire?

 I dont know much about the empire, but from what ive seen ive heard it was simply to big to hold, it was to wide to keep secure and control of and surrounded by potential enemies.

 Revolts were common especially in the east and the rise of the likes of Parthia and Bactria who broke away from the empire, the east was barely possible to control and after a revival of fortunes under Antiochus III he was defeated by Rome at Magnesia 190bc and after him civil war and invasions reduced the empire.

 My knowledge is scant so im sure others can give more info.

Better say the main reason of the decline of Seleucid empire were all these continuous civil wars. The defeat of Antiochus III from Romans had a large impact in the Seleucid empire, from the point that he lost all European territories and a part of Asia Minor which in combination of losing territorial possesions later, from Egypt, Parthians and Jews, the empire was limited quite noticeably (keep in mind that in the end of the reign of Seleucus Nicator, the empire was so huge that he had appointed as is said, 72 Satraps around his empire)

In the last century of the Seleucid empire existence empire we had many cases of successions who were largely disputed with result, outbursts of civil conflicts. The military forces residing in Antiochia along with the mob, played a quite significant role in the creation of riots and in the proclamation of the kings. 

Can you tell me any more information of ancienct Pontos?

KINGS OF PONTUS
Mithridates of Cius	337/6-302/1
Mithridates I	302/1-266/5
Ariobarzanes	266/5-c.255
Mithridates II	c.255-c.220
Mithridates III	c.220-c.185
Pharnaces I	c.185-c.170
Mithridates IV Philopator Philadelphus	c.170-c.150
Mithridates V Euergetes	c.150-121/0
Mithridates VI Eupator	121/0-63
First Mithridatic War, defeat by Rome, 88-85; Second Mithridatic War, 83-82; Third Mithridatic War, 74-63; Pompey's Settlement of the East, 63
Pharnaces II of the Bosporus	63-47
Darius	39-37? BC
Roman Province

But it was also frequently used to denote (in whole or part) that portion of the old Mithradatic kingdom which lay between the Halys (roughly) and the borders of Colchis, Lesser Armenia, Cappadocia and Galatiathe region properly designated by the title Cappadocia towards the Pontus, which was always the nucleus of the Pontic kingdom.

This region is regarded by the geographer Strabo (A.D. 1920), himself a native of the country, as Pontus in the strict sense of the term (Geogr. p. 678). Its native population was of the same stock as that of Cappadocia, of which it had formed a part, an Oriental race often called by the Greeks Leucosyri or White Syrians, as distinguished from the southern Syrians, who were of a darker complexion, but their precise ethnological relations are uncertain. Geographically it is a table-land, forming the north-east corner of the great plateau of Asia Minor, edged on the north by a lofty mountain rim, along the foot of which runs a fringe of coast-land. (...) Between the Halys and the Iris the mountain rim is comparatively low and broken, but east of the Iris it is a continuous lofty ridge (called by the ancients Paryadres and Scydises), whose rugged northern slopes are furrowed by torrent beds, down which a host of small streams (among them the Thermodon, famed in Amazon story) tumble to the sea. These inaccessible slopes were inhabited even in Strabos time by wild, half-barbarous tribes, of whose ethnical relations we are ignorant, the Chalybes (identified by the Greeks with Homers Chalybes), Tibareni, Mosynoeci and Macrones, on whose manners and condition some light is thrown by Xenophon (Anab. V). But the fringe of coast-land from Trebizond westward is one of the most beautiful parts of Asia Minor and is justly extolled by Strabo for its wonderful productiveness.

The sea-coast, like the rest of the south shore of the Euxine, was studded with Greek colonies founded from the 6th century onwards: Amisus, a colony of Miletus, which in the 5th century received a body of Athenian settlers, now the port of Samsun; Cotyora, now Ordu; Cerasus, the later Pharnacia, now Kerasund; and Trapezus (Trebizond), a famous city from Xenophons time till the end of the middle ages. The last three were colonies of Sinope, itself a Milesian colony. The chief towns in the interior were Amasia, on the Iris, the birthplace of Strabo, the capital of Mithradates the Great, and the burial-place of the earlier kings, whose tombs still exist; Comana, higher up the river, a famous centre of the worship of the goddess Ma (or Cybele); Zela, another great religious centre, ref ounded by Pompey, now Zileh; Eupatoria, refounded by Pompey as Magnopolis at the junction of the Lycus and Iris; Cabira, Pompeys Diospolis, afterwards Neocaesarea, now Niksar; Sebastopolis on the Scylax, now Sulu Serar; Sebasteia, now Sivas; and Megalopolis, a foundation of Pompey, somewhere in the same district.

Originally posted by Maju KINGS OF PONTUS Mithridates of Cius 337/6-302/1 Mithridates I 302/1-266/5 Ariobarzanes 266/5-c.255 Mithridates II c.255-c.220 Mithridates III c.220-c.185 Pharnaces I c.185-c.170 Mithridates IV Philopator Philadelphus c.170-c.150 Mithridates V Euergetes c.150-121/0 Mithridates VI Eupator 121/0-63 First Mithridatic War, defeat by Rome, 88-85; Second Mithridatic War, 83-82; Third Mithridatic War, 74-63; Pompey's Settlement of the East, 63 Pharnaces II of the Bosporus 63-47 Darius 39-37? BC Roman Province The small states of Armenia, Pontus, Bythynia, Pergamum, Cappadocia, Galatia, Commagene, and Caria testify to the ethnic complexity of Asia Minor. (...) Of the lists given here, only the rulers of Pergamum would actually have been Greeks. We can see non-Greek influences in the names of the multiple "Mithridates" of Pontus and Commagene. This name means the "gift," dates, of the Iranian god Mithra (Sanskrit Mitra). This is a Persian name whose modern form is Mehrd�d, of whose meaning many modern Iranians may be unaware. (...)

Mithridates of Kios wasn't actually a king, just a satrap from the Persian Empire. And Mithridates I Ktistes didn't take the title of basileus until 281.

Well Armenia took over the Empire under Tigranes the Great under Seleucid invitation and Rome conquered it from Armenia when Parthians allied with Romans opened an Eastern front and financed a rebellion within.