There is a general feature for those that awaken by consuming beast cores they will latter get to called it system and this system will give them quest and reward upon leveling up but the story evolves for a primitive era to an urban setting so pls stay tune for some ups and downs and some serious twists and turns.
Ranks are
RankF' (15/50) battle strength slightly weaker than Tier 1 beast
RankE (100/200) battle strength slightly stronger than Tier 1 beast
RankD (300/500) battle strength slightly weaker than Tier 2 beast
RankC (600/1000) battle strength slightly stronger than Tier 2 beast
Rank B (1000/5000) battle strength on par with Tier 3 beast and slightly weaker than Tier 4 beast
RankA (6000/10000) battle strength stronger than Tier 4 beast and slightly stronger than Tier 5 beast
RankS (1,000,000 and above) considered a threat to all beast.
Tier1 beast formally domestic and slightly wild beast
Tier2 beast formally heavy load animals that were used to work on farms and other jobs.
Tier 3 beast formally wild animals but not carnivores
Tier 4 beast formally wild animals highly omnivorous but not carnivores
Tier 5 beast fully carnivorous in all aspects very dangerous