There is plenty of loot to collect in the Realm, and plenty of monsters to take it from. Many of RotMG's players have provided awesome images and information and will continue to do so as content is continually added to the Realm.
Items from the Realm are grouped into "Tiers". The number in the left column indicates what "tier" the weapon is. If the item has "UT" in that column, then it is an untradable item that is only dropped by certain Foes and not found in groups among the tiers. The item with "L" in that column indicates that the item is of limited availability, and does not drop from any creature under regular circumstances.
Certain monsters have "tier group drops", where one random item of that tier has a chance to drop. Several drop locations for these grouped drops are listed on the below main categories' pages. Additional drop locations can be found in the specific item's page.
All tier 8+ weapons, T9+ armor, and T5+ abilities are now sold in the Nexus.