Annúminas is a majestic ruin in Evendim, the former capital of the Kingdom of Arnor which was founded by Elendil at the end of the Second Age.
Elendil and his sons escaped the downfall of Númenor (Sauron and those who worshipped Melkor, the original Dark Lord, tried to wipe out those who were faithful to Eru and the Valar). They took with them palantíri (seeing-stones) and the sword Narsil (a family hierloom from the First Age filled with power). The faithful survivors of Númenor became known as Dúnedain.
Their ships were separated in a storm so Elendil settled on the shore of Lake Nenuial in Evendim and founded Arnor while his sons (Isildur and Anárion) ended up further south-west and founded Gondor. They kept up communication by using the palantíri. Elendil was killed in the battle at Barad-dûr against Sauron and Narsil broke under his body. Isildur took the hilt and sliced Sauron's hand, severing him from the One Ring.
There were ten kings of Arnor. When the tenth king, Eärendur, died, his sons divided the kingdom between them. Amlaith, the eldest son and ancestor to Aragorn, founded Arthedain (which included regions now part of the Shire, Bree-land, North Downs and Lone-lands). His brothers founded the realms of Cardolan and Rhudaur. Annúminas was abandoned.
Glinghant - 6 person instanceThe gardens of Annúminas were located in the south-east of the city. The terraces have now been taken over by Angmarim and darkwaters who cast fear and spread disease to those who wish to visit.
Use the lever on the first terrace to start an event involving waves of mobs attacking. The second terrace has three stagnant oaks to defeat. On the top terrace, defeat Nengon and his fellow darkwaters.
Haudh Valandil - 6 person instanceThis was the tomb of Valandil, youngest son of Isildur and the third High King of Arnor. The sorcerors of Umbar want to raise Valandil from the dead as a powerful wight under Sauron's control. They have many minions who will try to stop you from returning Valandil's remains to where they belong.
Clear out the rooms with the Arnorian Knights and light the beacons to unlock access to the upper level. Shingrinder waits across a bridge. Beyond him, Dolvaethor sends waves of burning limrafn at you from behind a wall of fire. Once they're defeated, he runs away and sends Arnorian Wights to attack. At the top of the stairs, he waits with Valandil.
Ost Elendil - 6 person instanceThe throne room of Annúminas was located on the fortified island of Tyl Annûn in the north of the city. Balhest has claimed it for himself with Angmarim and Tormented Spirits to guard him.
The key to this instance is kiting the Morelendil Guards to the windows to allow the light to dispel their protective buff. Open windows by clicking the counterweights. You also want to avoid using fire, Common, Ancient Dwarf and Westernesse damage as the wraiths have a buff called Terrible Retribution which can reflect damage back at you. Without the light buff it may be possible to defeat Guloth by healing through the attacks by the Morelendil Guards and using other damage types (e.g. light, lightning, frost, Beleriand). In the throne room, you have to defeat all the guards before you can fight Balhest and his allies.
Note: The defeated mobs in these instances give rep with the Wardens of Annúminas.