They sensed the danger before it arrived and could have prepared to fend off the blood beasts. But they didn't do that.
They still decided to run because the amount of enemies was more than they could safely handle. They picked a direction that they predicted was the safest and rushed towards it.
Their action didn't deter the blood beasts, though. The rank 7 and rank 8 blood beasts chose to pursue Legion with everything they've got.
This chase lasted for hours. During that time, the slower blood beasts were left behind. Only the fastest blood beasts could keep up with them.
These blood beasts were three rank 8 ones. No matter how Legion ran, they couldn't be left behind.
After seeing that they couldn't filter the remaining blood beasts by dragging out the pursuit, Legion decided to fight them.
