The first level cap within King of Pantheon was at Level 100. Once players reached Level 100, they would receive no more EXP even if they farmed monsters, dungeons or even missions. Furthermore, their levels would be locked, and they would be unable to level up any further. The only way for the restriction to be waived is for the system to increase the level cap.
The level cap was implemented in order to appease future players. At the end of the day, King of Pantheon only had one server, and it would be released globally. If they had allowed the first batch of players to grind levels without any restriction, it would undoubtedly cause the newer players to lose their motivation to level up, as no amount of effort would enable them to catch up with the veteran players.
By implementing the level cap, they would be able to mitigate the problem by a great deal.
