Sockets/gems
Gear has empty slots into which players insert gems or runes that grant stats, effects, or abilities, adding a customization layer on top of the base item. Path of Exile famously routes its entire skill system through socketed gems, while Diablo II's runewords made socket combinations build-defining. Designers use sockets to let players tune and personalize found gear, to create a secondary progression and crafting system (leveling gems, combining runes), and to add build flexibility (the same armor supports different setups depending on what's slotted). Key decisions: socket types and color/link constraints (PoE's colored, linked sockets are a system unto themselves), whether gems are permanent or removable, gem progression (do socketed gems level up?), and how sockets interact with the broader itemization. Pitfall: sockets can become either trivial (just more raw stats) or bewilderingly complex (PoE's socket system is a notorious new-player wall) — the design must decide whether sockets are a light customization garnish or a core system, and scaffold their complexity accordingly.
- Dev effort: Medium
- Timing: Real-time or turn-based
- Common in: arpg