In TA 2989, Balin left Erebor and entered Moria with Floi, Oin, Ori, Frar, loni, Nali and a hunter named Aegrotus intending to establish a colony and reestablish the ancient kingdom, but the orcs of Moria discovered them and the colony was destroyed. 

During the battle of the Dimrill Dale Aegrotus acted as a Guard to Balin and along with the other dwarves fought off waves of orcs for a long time. Caught off guard Balin was struck with a single arrow from an Orc archer in the midst of battle. 

The loss of Balin proved too much for the battling Dwarves who were forced to flee from the Mines. 

Upon return to Khazad-Dum Aegrotus spent many a year searching for the orc archer until he finally discovered the Orc and avenged the death of Balin.

In his age Aegrotus still remains a keen hunter and fisherman and will often be found around lakes in even the most extreme areas such as Forochel.

In his time in Forochel he befriended Lossoth in Suri Kyla who in time sold him his young wolf-like pet dog which now is Aegrotus' most trusty companion and will be seen following him everywhere.