Imperial Legion

The emperor's muscle and the force of law and order in Vvardenfell. The Imperial Legion has seven Imperial garrisons: Fort Moonmoth (Balmora), Fort Buckmoth (Ald'ruhn), Fort Hawkmoth (Ebonheart), Fort Darius (Gnisis), Fort Pelagiad (Pelagiad), Wolverine Hall (Sadrith Mora), and Governor's Hall (Caldera). Note that all of these garrisons (with the exception of Wolverine Hall) are on the western part of the island.

Members of factions receive different types of welcomes from members of other factions, depending on how they get along. The formula is (Faction Reaction * 5)*(0.5 +(Faction Rank *0.5)). In plain terms, this means that as you attain higher ranks in your faction, people with negative modifiers will like you less and people with positive modifiers will like you more. This does not mean that everyone will start attacking you on sight, nor does it mean that they are going to fall all over themselves to be helpful. It does, however, modify their initial disposition toward you. This initial disposition will be further modified by your Personality, your overall reputation, your Criminal Status, whether or not you are Diseased, what kinds of favors you have done for the faction you're dealing with, etc. The other person may wind up liking you a lot or not liking you at all, but your faction and rank can impose a serious modifier.

Reactions to Other Factions
Hated Enemy
Beloved Ally (+3)
Camonna Tong
House Telvanni
Thieves Guild
Morag Tong Mages Guild
House Hlaalu
House Redoran
Imperial Cult
Fighters Guild
Imperial Legion

Advancement within the Legion will depend upon your skill level in three of the following skills:

Imperial Legion's rank structure:

Rank Endurance Personality One required Skill at Two other required Skills at Minimum Faction Rep Armor given
1 - Recruit 30 30 0 0 0 Imperial Chain Cuirass
2 - Spearman 30 30 10 0 5 Imperial Steel Shield
3 - Trooper 30 30 20 0 10 Imperial Steel Cuirass
4 - Agent 30 30 30 5 20 Imperial Steel Helm and Gauntlets
5 - Champion 30 30 40 10 30 Imperial Steel Pauldrons and Boots
6 - Knight Errant 31 31 50 15 45 Templar Cuirass and Greaves
7 - Knight Bachelor 32 32 60 20 60 Templar Helm and Bracers
8 - Knight Protector 33 33 70 25 70 Templar Pauldrons and Boots
9 - Knight of the Garland 34 34 80 30 80 Duke's Guard Silver Cuirass
10 - Knight of the Imperial Dragon 35 35 90 35 100 Chrysamere and Lord's Mail

Of course, these promotions don't come just based on your skills. You must perform quests to gain reputation and rank within the Legion.  Just ask about "orders" to anyone who has it in their conversation threads. General Darius at Madach Tradehouse in Gnisis is the only NPC who will allow you to join the Imperial Legion. The Imperial Legion quest givers are, in no particular order:

Typically, each rank requires two or three successfully completed quests in addition to the minimum stat and skills requirements. You cannot progress beyond Knight Protector until you talk to Varus Vantius. His first quest has two parts. You will be promoted to Knight of the Garland when you complete the first part and be promoted to Knight of the Imperial Dragon when you complete the second part. Your promotion to Knight of the Imperial Dragon should automatically kick off Vantius' second quest.

As an added benefit to joining the Legion, once you reach rank 8, you should have access to the various "Evidence" chests at the forts. The chests will still be locked, but picking the lock should not bring the guards down on you (you outrank them, after all) and you can retrieve any stolen items that the guards have taken from you.