Easter Island, also called Rapa Nui, is a remote island in the Pacific Ocean and one destination of the Avalon World Tour.
Easter Island is the current headquarters of Nokkar, an alien Sentinel sent to Earth to watch over it during his people's war with the Space-Spawn invaders. He arrived here in about A.D. 400, and befriended the natives, sharing his mission with them.  They built the moai in honor of him, modelling the statues' features after his own. After the natives died out, Nokkar continued to watch over Easter Island, alone. He met Goliath, Elisa, Angela, and Bronx when the Avalon World Tour brought them there in 1996. Upon leaving Nokkar had befriended three local humans on the island. ("Sentinel") He will remain on the island for centuries to come and continue to carry out his Sentinel work. In 2198 he will finally leave the island to battle the Space-Spawn. 
Real World Background
Its native name is said to be Te Pito o te Henua; its more familiar name was bestowed upon it by the Dutch explorer Jacob Roggeveen, who first sighted it on Easter Sunday in 1722 and named it "Easter Island" as a result. Easter Island is world-famous for its colossal stone heads, the moai, raised by its natives, which have become one of the world's great mysteries.
- Easter Island at Wikipedia, the Free Encyclopedia