Now that Sylvanas'  WoTLK Classic Gold base is gone, you can turn your attention to Silvermoon. Since they don't know you're coming, you have all the time you need to prepare your assault. Haunt the gold mine at Sylvanas' old base to generate extra income and start cranking out units. Silvermoon is very heavily fortified, and you'll have to cross a bridge to get to the city, which creates a serious choke point for your ground forces. Again, focus on crypt fiends and meat wagons, and this time add some extra gargoyles into the mix.

Spellcasters are optional but can help if you use them properly. With two gold mines and no opposition, you can go ahead and push all the way to the 90 supply limit. Once you've got a massive army, proceed to Silvermoon. You'll face an archmage that will cast blizzard and water elemental, along with a large force of footmen, archers, priests, sorceresses, and dragon hawks, so you'll have quite a battle cut out for you. After the first offensive at the bridge, you can push inward and start taking out buildings so the enemy can't reinforce its troops.

Once the enemy threat is neutralized, regroup your forces before you head to the sunwell. You'll need a lot of crypt fiends and gargoyles to take down the four level-nine stone golems guarding it, and several meat wagons firing from the back will ease the job considerably. The golems are immune to spells, so you can't use Arthas' death coil on them. He can help with his normal attack, but if he dies you'll have to resurrect him before you can finish the mission, so you may want to keep him out of the way. After you finally demolish buy WOW WoTLK Classic Gold the last golem, move Arthas onto the circle of power to resurrect Kel'Thuzad and finish the mission.