Codex of Power vs. Extracted Aspects
Codex Aspects are permanent and can be used multiple times, but their values are fixed at the lowest possible roll.

Extracted Aspects (from looted gear) are one-time use but Diablo 4 Items can have significantly higher values, offering a stronger boost.

Best Practice: Use Codex Aspects early to fill gear slots while leveling. Later, replace them with high-roll Aspects extracted from top-tier Legendary items.

Essential Aspects by Playstyle
Each class benefits from certain core Aspects that dramatically enhance performance:

Barbarian: Aspect of the Relentless Armsmaster (resource regen), Aspect of Ancestral Echoes (free skill triggers)

Sorcerer: Aspect of Control (bonus damage to crowd-controlled enemies), Aspect of the Unbroken Tether (Chain Lightning bounces more)

Rogue: Aspect of Corruption (enhanced Imbuement skills), Aspect of Quickening Fog (stealth and cooldown reset)

Druid: Aspect of the Rampaging Werebeast (Crit boosts), Aspect of Retaliation (damage scaling from Fortify)

Necromancer: Aspect of Grasping Veins (Crit synergy with Corpse Tendrils), Aspect of the Empowering Reaper (Essence generation)

Builds are often defined by these key Aspects. Choose ones that Diablo IV Items for sale synergize with your core skills and Paragon path.