Synonyms for Dampen:

n.

lessen, subside, erode, reduce, dilute, shrivel, chip away. soak, wring, saturate, squirt, hose, wipe up, dispirit. dampen (noun)
damp, muffle, weaken, mute, wash, moisten, tone down, dull, break, stifle, soften.

v.

change (verb)
stifle.
de-motivate (verb)
hamper, throttle, paralyze, impede, curb, de-motivate, hinder, frustrate, stifle.
deject (verb)
dismay, deject.
dissuade (verb)
avert, disincline, daunt, restrain, derail, check, dishearten, depress, dissuade, inhibit, prevent, deflect, deter, admonish, divert, chill, bar, intimidate, discourage, ban.
make wet (verb)
humidify, wet, sprinkle, spray, moisten, water.
moisten (verb)
spray, sprinkle, splash, moisten, humidify, wet, water, splatter.
spoil spirits (verb)
curb, deject, stifle, dismay, chill, mute, inhibit, depress, restrain, dispirit, muffle, discourage, dull, check.

Other synonyms:

wring, wipe up. hose, bathe. soak, saturate. squirt. depress
dispirit.
moderate
tone down.
moisten
humidify.
wet
wet.