This guide is mainly for those who don't plan to continuously buy an Upgrade, but want to optimize the perks even after its expiration. It is found impractical to list down all the benefits so that will be for you to research on. Try the Wikidot.
You can just click here for a list of items that are free to equip but require Upgrade to obtain. However, we've decided to highlight stuff that you should consider obtaining.
Enhancements
Be sure to hit the level cap so that you can use all the superior enhancements including those from the Blade of Awe. Even if your Upgrade expires, your items still keep the stats.
Primal Blade of Awe
If you have the Blade of Awe, you can evolve it for better looks.
DragonBlade of Nulgath
If you like a huge partly-color custom item, PvP and a challenge, try getting this huge weapon. It has some ridiculously difficult requirements, but the DragonBlade of Nulgath is an awesome item.
Legendary Hero
Now for the class identity of upgrade players. The Legendary Hero is a tank class that has a buff/debuff skills with an epic nuke. Check our guide for more info.
Ultra Elemental Warrior
While obtainable with about 2.4k ACs, there are better options for spending that amount. Why not earn it then obtain it with an Upgrade? The Ultra Elemental Warrior is a powerful class with decent PvP performance.
Beast Master
Unleash the beast! This battle-pet class requires an upgrade to obtain (whether AC or reputation) but you can still use it after expiration.
Badges
Having an Upgrade lets you access special areas that may offer you character page badges. For a list of those badges, click here.
Skyguard
Feel free to rank up Skyguard reputation. Try to get the free player items while you can still access the area.
Start a Guild
If you feel ambitious, you can start a guild. Use /gc <name of your choice> to create.
