Goblins had achieved much more than just crystal bombs over the years with Zhou Tian's support. Although crystal bombs were indeed the strongest weapons developed by the goblins at that time, with so many resources invested, it was natural that the goblins provided more than just a few outcomes for Zhou Tian. In fact, the weapons Zhou Tian gained were countless; it was only because some of these weapons couldn't keep up with the pace of his strength that, in the end, although it wasn't to say these weapons were useless, Zhou Tian had indeed only been able to store these weapons in a warehouse to gather dust.
However, as Zhou Tian could not return and needed his subordinate Beastmen to face the Human Emperor's forces alone, those Beastmen could then utilize those weapons.
