Current Arena Info
4E DnD Arena Monster Encounter Groups by Level
Below are the links to the monster encounter groupings by level. These groupings use a few abbreviations and some notation. First, the 4th Edition book that the group appears in is abbreviated, those abbreviations are...
Solo monsters (since they are not listed as encounters in the text) are set apart with boldface type.
So as an example, there's a level 12 encounter that looks like...