Preef was orphaned in a home robbery when he was just eight years old. The Nar Shaddaa orphanage was a living hell and it wasn't a coincidence a lot of those kids ended up working for the Hutts. So too did Preef get an early education in pickpocketing and it almost got him killed trying to steal from a Twi'lek bounty hunter.
The hunter admired the young Rodian's reckless courage and took him under his wing. For the next five years they wandered the galaxy in search of bounties, where he taught Preef the way of the blaster and for a few credits at a time brought him along to acquisitions.
It was a rough life and not without dangers. The Twi'lek trusted more in his own skills than in the protection of a guild and that proved to be his downfall. What was supposed to be an easy acquisition turned into a hellish blasterfight between hunters. Preef found the Twi'lek two days later on the plains, his Lekku's torn off and his corpse baking in the sun.
He never really managed to recover from that loss and filled with grief, loneliness and a desire to shoot something, robbed his first homestead. Six years later and he still hasn't moved on as he travels the Outer Rim, one small robbery at a time. Unfortunately his independent spree suddenly came to an end when the Crimson Dawn proclaimed that it owned him, having bought the young rodian in absentia from the Hutt Clan he ran away from eleven years ago.
[Below has been added through RP]
Preef had somewhat of a rocky start when he got back to Nar Shaddaa. Trying in vain to form a posse around a large slave-trading Trianni named Kholvar Varaxes, the young rodian saw himself often abandoned whenever Kholvar went offworld. Alone he didn't do so well and often got drunk on sewer-riped Nal Hutta moonshine until Marissa Hesse, a member of the Black Sun, approached him for a job as gunslinger in a casino robbery on Canto Bight.
With just the two of them, Preef and Marissa, robbed a Canto Bight casino and got away not only unscathed, but with a decent haul and a reputation boost. Not able to completely abandon his adoration for Kholvar, Preef quickly relapsed into his moonshine addiction once he realized the big cat had still not returned to him and in one of his many bad-remembered nights out got hold of a bounty fod. Trying to rebound, he decided to hunt down the two wanted men (both members of the Black Sun) with the help of the protocol droid V3PO in order to join the Bounty Hunter's Guild. The idea of becoming a bounty hunter, much like the Twi'lek that had rescued him from the Shaddaa gutters a decade ago, felt a bit like a homecoming that the rodian readily gave into.
Ofcourse, that didn't meant he was suddenly free of the Crimson Dawn. After all, they literally owned him. In order to keep paying his dues, Preef once again paired up with Marissa Hesse to break a high-up confident of the Five Syndicates out of a prison ship belonging to the Free Worlds Alliance. They were hardly done when the four of the five syndicates banded together against the Pykes and send both Preef and Marissa to Kessel. Wars in the underworld were fought differently than between worlds or government, however, and three weeks later there was once again peace. The conflict was costing all parties too much money for them to continue.
After that it was quiet for a bit. Preef had cemented a reputation in the Outer Rim and acquired a small fortune in credits. The latter he spend on a small prefab ranch (and some cattle) on the Mid Rim world of Takodana. It became his refuge and a place where he learned to reflect on the life he's lead. He was twenty-one when he was forced to join the Crimson Dawn, penniless and filled with regret and an unsatisfied desire for revenge, and now, three years later at twenty-four, he was definitely changing.
Some time later Marissa and Preef decided it was time for them to leave the umbrella of the Five Syndicates. More specifically: the growing working relationship between the syndicates and the reemerging Sith Order and "Sith Empire" made even the slightest association with the syndicates a painful risk. To fund their retirement, or rather their future business ventures, they started robbing from the Five Syndicates and did so with impunity. No one dared to go after them while Marissa's wits and Preef's blaster were together. Marissa was per chance arrested by the Sector Rangers in the Core, but before they knew who they were dealing with the Sith attacked Coruscant and Preef used the chaos to not only help Marissa escape, but also raid the Sector Ranger's evidence vault.
After the spree of armed robbery Preef retreated to the Tasthor Sector and his ranch on Takodana. He had enough credits to retire, it's just... well, he wasn't the retiring age just yet. Then the winds changed and an opportunity arose for him to become part of the Crymorah Syndicate in a place where their work could remain under the radar of the Sith and the risks they brought with them.
Preef Callo is a Rodian of below average intellect who has only ever known a violent lifestyle. He knows of no other way of conflict resolution than blaster violence and cares little for the lives of others. That doesn't mean he prefers solitude, however, and he is known to burn surplus credits at Pazaak, Sabacc and to female companionship. Likewise, he prefers to bring other outlaws on robberies and is known to have been a member of several posses in the past years. Due to his wandering and solitary lifestyle he isn't known as a member of the Crimson Dawn and he rarely associates with them, simply not understanding the majority of their crimes. Preef is a blaster, not a thinker.