Cool, just for clarification, is it supposed to be a frog mech or a spider mech?  And you listed the Colossus theme as 'transforming', so does it transform by itself into a humanoid mech or something, or is that in anticipation of it combining with another Colossus?  You can also include  real-life military weapons: missiles, cannons, machine guns, etc., even near-future technology like lasers and such.  I like the poison idea, though I might ask that you change it to acid, and maybe merge it with the slime, like it shoots out an organic mucousy acidic net to trap monsters.

Just some suggestions.