Being an endgamer you have very little use of the regular souls, 5 a day for the daily challenge, and they drop in numbers. Especially in the dungeons.
You can only get rid of them by opening them and then sell the trash. You can ofc keep them and stack them for later use, but at some point you reach the the limit and MACLO will kick you just when you think you just won a fight. Or maybe you can't purchase stuff from the game store.

I suggest a Soul Converter. You take, lets say, 25 regular souls and put them in it. And then you'll recieve a rare soul.
Or you put in 20 rare souls and recieve a Legendary Soul.

Just my 2 cents