Adeste came from a poor family/village, and growing up saw how hard her family worked to keep a roof over their heads/food on the table. So as soon as she was old enough, she enlisted into the military in order to try and earn gold to send back to them. She started in the lowest ranks obviously, but her stubborn, relentless nature on the battlefield, and laidback/cheerful nature during down time steadily helped her rise through the ranks until she was given command of a small group. For her first mission as a leader, she was tasked to rid an area of the land of a monster terrorising the small villages (which coincidentally her old home village was one of them). Adeste proudly went to battle the beast, however she made a mistake, a terrible one that cost the lives of over half of her men, along with several innocents, including her own mother.
 
Adeste was able to help the remaining survivors escape, but the shame and horror of the cost of her mistake hung heavy. Instead of giving in, or going back a failure, she swore vengeance on the monster, and snuck away from their encampment, armed only with her halberd and armour, prepared to sacrifice her own life to end the beast if it meant her vengeance would be fulfilled. Surprisingly, Adeste survived - perhaps a god smiled upon her that day and guided her strikes, or perhaps it was just luck. The monster was slayed, vengeance was wrought. She returned to the capital a hero despite the losses, and was gifted a new halberd to mark her ascension into higher ranks of the military - an enchanted weapon of sentience (bringing in that warlock side)
 
Over the years after that Adeste continued to serve in the military with unswerving loyalty. However she never forgot the origins of her success. She pursues her enemies relentlessly, and will not rest until she sees them dead. The only thing that can sway her from her course once given is the suffering of innocents - particularly if they suffer from what ever new target she has been sent to destroy, in which case she will gladly take time to try and help them. Adeste has gained a reputation of being dutiful and charitable, and a fun presence to be had when relaxing with a drink and food, but a terrifying force on the battlefield - the risks she is willing to take to protect her allies, going so far to actively encourage the most dangerous enemy to target only her, has earned the respect of her subordinates and colleagues, alongside her ability to take a joke now and then.