Gargoyle

Broadly and in real life, a gargoyle is a weird-looking stone figure built into/atop a building or other structure, nominally as a water drain to get rainfall to run off the top of the building. (See this Wikipedia article, which makes the point that a weird-looking stone figure built into/atop a building that doesn't carry water is more properly termed a "Grotesque." Picky, picky.)  In the Girl Genius context, the gargoyle is the particular weird-looking stone figure that Carson von Mekkhan engages in one-sided conversation about the latest pretender to House Heterodyne. The conversation occurs here, and from it one might deduce that old Carson is getting a bit dotty, what with "conversing" with weird stone figures and all.

However, one would be wrong to thus deduce. This isn't any old gargoyle, but rather a Construct of as-yet unknown capabilities. How do we know that? Well, when Agatha,  Zeetha,  Krosp, and Ardsley Wooster first come to town and strike up a conversation with Herr von Mekkhan, the gargoyle notices and follows them with a turned head. Von Mekkhan sees this and decides that another interaction with the party is called for -- and we know how that turns out.

This gargoyle may well have some combat skills in addition to the ability to recognize a Heterodyne when it "sees" one. Carson muses on the likelihood that the Heterodyne pretender (by whom he really means Zola "Heterodyne", not Agatha, who's still unknown to him at this point) has some backers who could be trouble, and tells the gargoyle that he "expect(s) you'll help me deal with them." The tenor of the "conversation" suggests that "dealing with them" will have hack-and-slash implications. This combat hasn't yet come to pass, but patience...