Aside from the "Collector" achievement/trophy, completing the Codex gives you a much deeper understanding of the Star Wars canon between Episode III and Episode IV. It explains the origins of the Inquisitors, the fate of the Nightsisters, and the hubris of the ancient Zeffo—stories that are only hinted at in the main cutscenes.
You don’t need to spend a dime to complete your collection. The game provides two primary ways to gather entries: 1. BD-1 Scans
This is the gold standard. Fans have manually transcribed every Databank entry, including the "Tactical Guide" which explains enemy weaknesses.
Websites like MapGenie offer free interactive maps that show the exact location of every scan and Force Echo you might be missing. Why Completion Matters
The deep lore of the Zeffo civilization and the Jedi Order.
If you’ve finished the game and missed a few entries—or if you just want to read the lore without booting up your console—there are several community-driven resources that offer the full text for free: