The Drain Monster bonus round rule is one of the many rules that can be applied during the Bonus Round episodes. It is offered when either entering floor 4 or 5 as long as either of these conditions are met:

• Drake is the boss of the dungeon
• At least 2 of these 4 enemies are in the dungeon:
  • Haunted Jar
  • Drain Monster
  • Dire Wolf
  • Rat King

It is not offered if the Warlock bonus round rule is active.

Drain Monster

When Poison deals damage, it also inflicts 1 weaken.

When the rule activates, both fighters in each fight will gain a permanent innate status that makes it so that any Poison damage taken will also inflict 1 Weaken as well.

This rule applies to both player and enemy, and since Poison isn't easily reducible, can ensure that some equipment is consistently weakened. It's also the only way for poison-using enemies like Drake and Rat King to weaken equipment, like Wooden Stake.