Meta gems: Meta gems are special types of skill gems that and can be supported by both support gems and other skill gems. Meta gems can trigger skills or provide more complex effects. Most trigger meta gems activate the supported gems when you fulfill the condition enough times.
Items no longer contain sockets. Instead, the gem menu contains 9 slots for skill gems or meta gems.
Support gems can be socketed into skill and meta gems. Support gems now no longer provide raw more damage modifiers, and instead are purely focused on utility. Support gems now add stat requirements to the skill gem’s base attribute requirements.
Spirit: A new resource called Spirit is added in addition to Life and Mana. Spirit is used to reserve skills with persistent effects like buffs and auras, upkeep permanent minions, and enable trigger meta gems. Spirit can be increased through story boss rewards, modifiers, and sceptres.