The Area Level is what determines the item level of any Gear you drop. The item level attached to the gear determines what modifiers can roll on the item and the tiers of those modifiers. Plainly said, the higher your area level the more powerful items you will find.
The Area Level also determines the type of gear you will see. For example you would no longer want to see early game items such as Wooden Swords once you are far into the late game so these items will be much more rare, but will still drop.
The Overworld will have a set area based on the highest difficulty boss you have completed and then Explorable Maps will have the area level of the map based on the tier of the map.
| Boss | Area Level |
|---|---|
| (DEFAULT) | 5 |
| King Slime | 10 |
| Eye of Cthulu |
15
|
| Eater of Worlds | 20 |
| Brain of Cthulu | 25 |
| Queen Bee | 30 |
| Deerclops | 35 |
| Skeletron | 40 |
| Wall of Flesh | 45 |
| Any Mech Boss | 50 |
| Plantera | 55 |
| Golem | 60 |
| Ancient Cultist | 65 |
| Moonlord | 70 |
| Tier | Area Level |
|---|---|
| 1 | 52 |
| 2 | 54 |
| 3 |
56
|
| 4 | 58 |
| 5 | 60 |
| 6 | 62 |
| 7 | 64 |
| 8 | 66 |
| 9 | 68 |
| 10 | 70 |
| 11 | 72 |