Currently, the Berserk energy is eating is from the Monster stage monster core, In the past it was enough for mutation as it was able to grow till 2% because of it but now it isn't enough for mutation to grow, now it needs something more, a little more powerful than Berserk energy provided by the Master stage Core.
Its not like I've not thought of this problem in the past few days, I've thought that but I was powerless to do anything until I created five seals today.
Till today I had been using Master stage monster core berserk energy because my body can't handle Liutenent stage monster core berserk energy.
I've had eaten an extremely small piece of Lieutenant stage monster core two days ago and it had injured me quite a bit as the berserk energy inside it quite intense.