Indiscriminate consumption of the Blood of Madness was a rule set by the Undead at the beginning of their actions, as disorder and automation are the greatest taboos in team battles.
It's okay if the damage output can't keep up, as long as no foolish mistakes are made.
However, with Lind's entrance, feeling the challenge the current BOSS posed, the Undead had no choice but to use all the means available to them, otherwise, they would fall behind in the battle's rhythm.
Serene, the lord of the Blood Lambs, recognized at a glance they were drinking the Blood of Madness, but as the master of the Blood Lambs, he owned the most of them. These mutated monsters had a low survival rate, were frail, unruly, and could not be tamed, cunning, and unpredictable.
Where did this group of Two-Headed People get such a large quantity of the Blood of Madness?