Kaltdrache lived in Angmar for 100,000 years since SA 1075. When Kaltdrache heared that Sauron was defeated at the Battle of Dagorlad. Kaltdrache waited in his lair for a long time until in TA 1300, when Kaltdrache heared the Witch-King, Rogash, Morgomir, Gorkil & an army of Goblins arrived to Angmar.
Kaltdrache freed the Snow Trolls & joined forces with the Witch-King. Then when the Black Númenóreans were crushed, the Black Númenóreans decided to joined with Angmar & so Kaltdrache used the Hill Trolls, Snow Trolls & Mountain Giants to fight for him.
Assault on Rhudaur
When the Witch-King was next going to assault Rhudaur. Kaltdrache was supposed to come when the Witch-King destroyed the first Arnorian camp on the hills. A group of Hillmen of Rhudaur begin to rebel against Arnor, led by Hwaldar. Hwaldar is seized and arrested, but Morgomir recognizes a valuable ally to control the Hillmen of Rhudaur. The Witch-king and his army eliminate the Loyalists and recruit the rebels. Soon after, they destroy the Dúnedain guarding Hwaldar and free him. They then proceed to attack the mighty Arnor fortresses in Rhudaur, but the attack (while successful on one fortress) weakens the Angmar forces badly and King Argeleb I soon arrives to finish them off.
Just as King Argeleb I was going to kill the rest, Kaltdrache comes & saves the remaining forces & kills Argeleb with his claws & flames. Morgomir brilliantly trains the Thrall Masters to replenish the Angmar army and wipe out King Argeleb's army. They then destroy the other fortress, claiming total control over Rhudaur & the Rhudaur Hillmen now have camps on their hills.
Fall of Amon Sûl
After Rhudaur was claimed by Angmar & armies of Goblins, Hillmen, Black Númenóreans & other units, The Witch-King builds more units to help Angmar destroy a Great Fortress of Arnor of a place knowed as Amon Sûl. Further invasions from Angmar are thwarted by King Arveleg I, who uses the Palantír of Amon Sul to foresee attacks. To proceed in Arnor's destruction, the Witch-king must destroy Amon Sûl and claim the Palantír.
Rogash, Hwaldar, Morgomir, Gorkil, Kaltdrache and the Witch-king are all involved in this battle. The forces of darkness start off by destroying five Mallorn trees that power various defenses of Amon Sûl. After they are destroyed, they proceed in destroying the walls. Reinforcements of Arnor later arrive, but the enemy units wipes them out completely. The Angmar forces turn back towards Amon Sûl and begin destroying the structures in the fortress despite heavy resistance. Angmar eventually summons two Mountain Giants and proceeds to attack the watchtower & the Great Fortress, destroying it once and for all.
Though Angmar has destroyed Amon Sûl, Arveleg has escaped with the Palantír. The Witch-King sends Morgomir to retrieve it.
Morgomir captured all six Palantír shards & managed to destroy the Arnorian Camp on The North Downs with his armies of Dark Rangers & Hill Trolls. Now the Witch-King now moves to Cardolan's most sacrred place of all, The Barrow Downs where their Great Kings of Arnor lie inside the Barrows. The Witch-King now neads Hwaldar to stand on top of the Royal Barrow. Cardolan wasn't affected by the destruction of Amon Sûl so the Witch-king attacks the Barrow Downs, planning to draw out Cardolan's forces into a foolish and self-destructive charge. He sends Hwaldar to claim the royal barrow. To assist the conquest, Hwaldar destroys the attacking forces and kills some Dúnedain rangers that planned attack the reinforcements of Angmar. With him are some Thrall Masters and Sorcerers that have gained power from the Palantír shards. When Hwaldar reaches the Royal Barrow, Cardolan becomes enraged and sends its forces to destroy him. But, the Rhudaur Spearmen & Axethrowers hold back each attack and the Sorcerers cripple and destroy Arnor's soldiers, turning some of them into corrupted Wights. As time passes, more Sorcerers, Thrall Masters, Dark Rangers, Black Númenóreans and Trolls (Snow Trolls & Hill Trolls) arrive; at one point, Morgomir joins the battle. In the end, the Prince of Cardolan himself arrives to answer the challenge, but so does the Witch-king, Rogash, Gorkil, Drogoth & Kaltdrache at the same time. The Prince is eventually killed by the Witch-King and his forces, and Cardolan is laid bare to the enemy.
The Great Plague (Return of the Barrow Downs)
After an unsuccessful attack by Men and Elves on the fortress of Carn Dûm, the Witch-King contemplates his next move. The audacity of his enemies angered him greatly, and a example should be made. However, Angmar has been significantly weakened, and his next attack needs to be planned in order to prevent failure.
With the help of Morgomir & Kaltdrache, he decides to unleash a terrible plague upon the unsuspecting Arnor, created by his sorcerers. These wicked men, already deeply immersed in the Dark Arts, have become even more powerful due to acquiring the shards of the Palantír; their powers have already been demonstrated in the Battle for Cardolan. However, the Witch-king needs a ground zero from which his diabolical plague will spread. With utter malice, he chooses the most sacred ground in all of Arnor: the Barrow downs. These quiet and dignified monuments of the Dúnedain are essential to the morale of Cardolan, which Angmar is perfectly aware of.
Morgomir & Kaltdrache is to lead the attack on the Barrow downs again. Cardolan's forces, outraged at this desecration, sends its own armies (led by Captain Carthaen) to destroy Angmar's forces even as the Sorcerers begin corrupting souls. Morgomir, however, instructs his Sorcerers to cast their own terrible spells on the Cardolan army, weakening it significantly. To finalize victory, Morgomir summons a tortured, evil ice werewolf to crush the opposition. The Sorcerers complete the plague, and the Barrow Wights are fully created. Captain Carthaen is soon trapped by the Wights, and Morgomir stabs him with a Morgul-blade. And so, Karsh the Whisperer is created.
Battle of Fornost (The Final Fall of Fornost)
Angmar has almost completely dominated Arnor, but Fornost still remains to be taken. The Dúnedain and their allies all gather for this final assault. In order to prevent a foolish advance (and subsequent destruction), the Witch-king prepares a base and gathers his forces first. After all the preparations, they begin the assault. Angmar starts by destroying the front gate and some of the outer defenses. Combining the fury of the Angmar army and deadly Angmar ice powers, the Witch-King slowly wears down the fortress one building at a time.
Over night, the armies of Angmar outaken the first outer defenses. Casualties are both sides are high as the Dúnedain desperately battle for their lives and Angmar's army fights in a berserk rage. In the end, the citadel of Fornost is destroyed and the structure falls. Angmar has achieved complete victory over Arnor, and has now opened the opportunity for complete domination of the North. The Fall of Arnor was over