I also hatched Sloth, but there is no new "goal" for the next rounds. Now I am at 110th fight, soon I will finish the second part (10 more fights to go), I will report the last one, and when I succeed, will post more info/pic.
Edit: one more thing. At every 5th step there is a special reward; more money, more food or a couple of stamina. It is not showed on the map, but every 5th step from 41-120th fight contains some special reward. Also, these steps have the hardest enemies, so prepare..
I finished almost all my fights with my lvl 10 Vinotaur. This monster was my very first breed in this game...
Edit: lvl 115 is a fight against a crystal unicorn reward is 5 gems, also food and coins