I can help with this one. It's not much of an argument, but I can maybe give an outsider's opinion of it, considering I don't know you IRL.
When most people create a villain, they do it for the shere reason of making the main character's life a living pain in the butt. Alot of times, this villain has no real reason to be bad except for the shere fact "they were born that way." Most people want you to concentrate on the hero, and not have any like for the villain, so they tend to gloss over the deeper intricatcies of the villain's personality and plot, so you don't develope any feelings or understanding. You just want him to be bad. The best example I can come up with for this sort of villain is Shaun Yu in Disney's Mulan. He basically just wants to kill the emperor for the fact that "Oh, he hurt my pride." That's about as deep as it goes. All you see him doing is killing and hurting, and haveing no real reason for it. He is such a two dimensional character, that people instantly just forget he's there. He isn't a villain, but a simple plot device. This tactic can work well in a movie setting, where you have to keep an audience amused for an hour and a half, but when it comes to a webcomic, where long term goals need to be accessable, it can spell certain disaster.
Grandma is a webcomic Shaun Yu. She has no real reasons for world conquest except for the fact that it makes the main characters do
something. No one knows why she is there, no one knows what drove her to do such things, and no one even knows her real name. (yes, I know that's not the point, but I was on a role.
) I think what needs to happen is that very soon we need to have some sort of plot sidestory that would explain a few more aspects of what is going on with Grandma. Today I read the most current comic (2/13) and it occured to me that you have the perfect
lead up to a bit of explaination on Grandma. Theo just mentioned that his father knew and worked with Grandma, but they had a falling out. I would reccomend using the next few strips to have Theo go into a bit of a storytelling mode with something his father told him about Grandma. About working with her. About the type of person she is...maybe even the fact that Theo's father was there when Grandma went bad. The one thing I have noticed is that alot of the characters have tended to be 2-D, and the plots (though you have gotten MUCH better in the past few months) have been placed as a factual "this is how it is" sort of basis. As a reader myself, I cannot stand to sit and read a comic that basically forces the readers to take the story for granted, and not explain how everything got there. This may work for a few one-joke a day comics, but 13th Labour is too involved for that. But, going back to Grandma, I could issue a few questions you could answer to help define who she is, and to make her a more beliveable villian.
1)Who is she?
2) What was her past (how was her childhood)?
3) Who did she marry to have Cecilia? How did she react to finding out she had Grandchildren?
4) What was her personality as a child?
5) Why was her personality drastically changed (if applicable) or, if she has always been so bent on running the world, how was she raised to get her to this point?
6) Why does she want to take over the world? Is it really because she just thinks she can run it better?
7) How does she feel about her grandchildren turning into strange creatures?
8) Why is she doing what she is doing?
9) What is her favorate color?
10) Other then piranas, does she have any other pets?
11) What happened to her husband?
These are a few questions to ask yourself. I hope I've helped out a bit.