What is a Monster Enhancer for the purposes of Mate?

[MunchkinMan]

The rules describe Monster Enhancers this way (with my added emphasis):

Originally Posted by The Rules, p. 5, Monster Enhaners

Certain cards, called monster enhancers, raise or lower the combat strength of individual monsters.

So, the cards that say that they are +X to the Monster would be considered Monster Enhancers, but not Treasure cards that aid the Monster side. The wording on the Mate card was actually designed to exclude one-shot Items, since it got very confusing what got doubled when a player played Mate on a Monster when there were already multiple Monsters and one-shot Items in use for the Monster side.