Thanks for the chapter!
MC is lucky Draining Touch worked. The usual trope for drain/life steal skills/abilities is it only works on living beings (positive energy) for stealing life/hps/energy and energizing/recharging the user. However, if used on a non-living being with no energy (golems or equivalent,) nothing happens. While undead (negative energy) either drains the user and boosts the undead or due to draining opposing energy the user loses energy, dies when hits zero, and has a chance of becoming undead themselves. (User being alive with positive energy gets weaker and/or dies due to absorbing negative energy from undead. If drains too much negative energy turn into a negative energy undead as well. So let's say alive positive energy user at 50hps of 100 drains 20hp per sec from an alive positive energy bandit then after first second will be at 70, 2nd second at 90 etc. However, if user at 50hps drains -20hp per sec from a negative energy vampire then would be at 30hps after 1 sec, 10hps after 2 secs, and -10 at 3 secs. Would die due to being at zero or less hps, and chance of turning into some kind of undead due to -10 points of negative energy although just more likely to turn into undead, not guaranteed. )
Wonder if that sword has some special or magical properties other than being a strong durable blade since came from the Maou as interfering with vampire's regeneration and dusting the bats, although lucky it's not cursed.