Upgrading System for Equipment

In you base should be a special merchant.
You can give them artifact weapons to unleash there powers for an offer.
The Equipment has several slots which can be unleashed.
e.g.: for a sword: blade, rune, spell
if you have unleashed all slots it gets a little upgrade for free.
and allows you to unleash its full power for a special offer.
The drops of the boss creeps can only be reanimated, so they can only be upgraded once.

More funny are the sets.
Some are buyable some dropps by the boss creeps of the capture points.
If all parts of a sets have there full power you can combine them to a set.
If you fullfill the right conditions e.g.: being a meele hero, being an agility hero and/or belong to the Hated.
Then you can equip the set, it uses all your inventory space and changes your model, also increasing your stats very high and grant you a special spellbook.
You can also upgrade a set one time, if you then equip it you get another hero and can't change back.
The heros have higher stats and better skills than normal heros but they start at lvl 1 again, making you a potential victim at the beginning, and a fearsome enemy at the end.