He was still in his egg when the lab was seiged by the monkeys, Bersal was yet another biological creation, following the success of the previous 2. The monkeys got into the lab and drove out the bloons, they decided to take the egg and see if they could learn about the bloons plans from it, unfortunately a high powered shot completely punched through the machine used to create the egg, the whole machine was wrecked. So this was the only egg they had, and through what they salvaged they uncovered what they believed to be the name of this creation "Bersal".
They took this egg back and soon it hatched, they found a strange centapede like creature. They realised it was obvious that this was made for combat, so soon they started training it to fight bloons and not attack the monkeys. It was a success, Bersal soon became very strong, his powerful jaws proved capable of tearing through bloons and even ceramics.
Bersal is a Bloon created centapede, captured by the monkeys and trained to fight bloons rather than monkeys, in a level only 1 can be present at any given moment, as there is only 1 Bersal.
He only has 2 upgrades, but he is very powerful anyway, because there is only 1 Bersal and there is no reason he would really need to get rid of them, once he has an upgrade he will have it forevar.
His jaws are capable of crushing lead and ceramic highly effectively and they can be quite painful to moabs, he is also capable of moving around the map, the player can even take direct control and move/attack with him.
Other uses[]
Bersal is actually capable of taking (or at least trying to take) land, so in BMC and simular things once you have him helping you he can be sent to try to capture territory, however decent players will be able to do better and he can't be relied on for complete automation (seriously, he's just a giant centapede! What do you expect?).
He's capable of creating towers himself (but he uses money to do this, just like the player. Which is why you don't see him creating towers when he assists you, however you can allow him to create towers himself).
But because he makes stuff, in things like BMC he uses up your towers.
Upgrades[]
1: Bersal is equipped with a glue gun, the use of this is quite obvious.
Requirements: 23000 total pops by Bersal and a glue gunner (the glue gun he's equipped with is the same as what the glue gunner had)
2: Bersal can create turrets like a monkey engineer can (however these are deployed at a significantly lower rate but they last longer than normal)
Requirements: 37500 total pops by bersal and a monkey engineer (if the engineer has any turret affecting upgrades then the turrets bersal makes will have that too)