Wanton destruction is appropriate only in moderation. Move Mountains and Shatter took advantage of pre-existing damage and amplified it. There's more than enough of that in the Geneforge world, so it shouldn't be too much of a problem to apply tactically. Or better yet, a disaster unique to this world: the genemodded plants, all to willing to usurp any building or clearing left alone for long enough. How about a new spell, Overgrow? Used on a section of forest, it would perhaps cause (young, breakable) trees to sprout up, barring your enemies path or even trapping them where they stand.