Artus is a gargoyle of the Manhattan Clan.
Artus will hatch in the Manhattan Clan's rookery in 2018.  He is the eldest of Broadway and Angela's three biological children, and older biological brother to Gwenyvere and Lancelot. Little else is known about him besides the fact that of Broadway and Angela's three biological children, he is the most likely to be aware of his parentage due to the few eggs in his rookery generation. He will not, however, be the only egg in the Manhattan Clan's 2008-2018 rookery. 
Greg Weisman has hinted that Artus will most closely resemble Broadway and Hudson, though most likely will have certain traits from Angela's bloodline as well. 
Real World Background
Artus is a French form of the name "Arthur", particularly used as the name of King Arthur Pendragon in medieval French literature. The combination of this name with that of "Gwenyvere" for his sister and "Lancelot" for his brother would suggest that King Arthur will have some very strong significance for the Manhattan Clan or some of its members. This probably is not surprising, however, in light of how the legends about King Arthur and Merlin inspired Broadway to learn how to read, the fact that Angela was brought up on Avalon, and that both have met King Arthur himself.