Skill Variants: Diablo 2 Rune Energy Returns

Perhaps the most exciting feature is the introduction of Diablo 4 Items skill variants.
Instead of the current structure - one mandatory upgrade followed by a choice between two modifiers - the new skill tree includes:

Two side paths with circular upgrades (likely smaller bonuses)
A central path with 3-4 boxed "Skill Variant" options. These variants appear to dramatically alter how abilities function.

Element Swaps and Gameplay Changes

In early previews, we saw:

Ball Lightning transformed into a ground-based fire skill
Frost Hydra variants
Lightning-based Incinerate
Elemental swaps across multiple skills

This system feels reminiscent of Diablo 2's rune system, where a single rune could completely redefine how a skill functioned - changing its element, damage type, or behavior.

If every skill in the game gains multiple meaningful variants, we could see:

Elementally flexible builds
Hybrid archetypes
Entirely new playstyles within existing classes

And according to Blizzard's description, even more cheap Diablo IV gold variants unlock through progression systems like "Lord of Hatred."

This alone could be the largest build diversity expansion Diablo 4 has ever seen.