For specific RuneScape monsters, check online guides - they tend to be pretty good. Apart from the guides on the RuneScape website itself, there are guides at runescape.wikia.com, tip.it, and others.
He is found in the Godwars dungeon, as he is the Zaros boss. Nex is currently the most powerful boss on RuneScape, so be careful.
There is no "best" armor in runescape, but armor such as the "nex" armor (Torva, Virtus, & Pernx) are some of the more elite types. Nex armor is dropped by the monster Nex in the gwd.
You cannot solo attack Nex. It must be a large group of people, soloing it has never been done so far.
You buy them in the TzHaar shops. It is also a very rare drop from Nex, and Kingly Impling.
CONJECTVS VNVS, NEX VNVS or in a modern representation: CONJECTUS UNUS, NEX UNUS
The best monster to kill in Runescape would be the King Black Dragon.
For members it is a 138. For free to play it is 126. The highest levelled monster, Nex, has a combat level of 1001.
For lower levelled players, consider doing slayer until the point they can kill blue dragons. For medium level players, consider 85 Dungeoneering for Frost Dragons. For high level players, the Kalphite King and Nex would provide a bit of end game PvM. All of these would give a nice amount of experience and gp per kill.
Nex was created in 2010.
It doesn't.
Nex Aviation was created in 2007.
The population of Nex Entertainment is 175.