dampener

Plural: dampeners

Noun

• One who or that which reduces intensity or moistens.
• a device that dampens or moistens something
  • "he used a dampener to moisten the shirts before he ironed them"
• A device that moistens or dampens something.
• A discouraging event or remark.

Examples

• The opponent’s relentless blocking was a real DAMPENER on my bingo dreams.

Synonyms

moistener, buzzkill, killjoy, party pooper, spoilsport