As a sell-sword who fought battles for coin, you're well acquainted with risking life and limb for a chance at a share of treasure. Now, you look forward to fighting foes and reaping even greater rewards as an adventurer. Your experience makes you familiar with the ins and outs of mercenary life, and you likely have harrowing stories of events on the battlefield. You might have served with a large outfit, or a smaller band of sell-swords, maybe even more than one.
Now you're looking for something else, perhaps greater reward for the risks you take, or the freedom to choose your own activities. For whatever reason, you're leaving behind the life of a soldier for hire, but your skills are undeniably suited for battle, so now you fight on in a different way.
Source: Sword Coast Adventurer's Guide
Skill Proficiencies: Athletics, Persuasion
Tool Proficiencies: One type of gaming set, vehicles (land)
Languages: None
Equipment: A uniform of your company (traveler's clothes in quality), an insignia of your rank, a gaming set of your choice, and a pouch containing the remainder of your last wages (10gp)
Countless mercenary companies operate up across En. Most are small-scale operations that employ a dozen to a hundred folk who offer security services, hunt monsters and brigands, or go to war in exchange for gold. Some organizations have hundreds or thousands of members and can provide private armies to those with enough funds.
You know the mercenary life as only someone who has experienced it can. You are able to identify mercenary companies by their emblems, and you know a little about any such company, including the names and reputations of its commanders and leaders, and who has hired them recently. You can find the taverns and festhalls where mercenaries abide in any area, as long as you speak the language. You can find mercenary work between adventures sufficient to maintain a comfortable lifestyle.
Use the tables for the Soldier Background as the basis for your traits and motivations, modifying the entries when appropriate to suit your identity.
Your bond could be associated with the company you traveled with previously, or with some of the comrades you served with. The ideal you embrace largely depends on your worldview and your motivation for fighting.