Well, Mummies have identical stats to Gargoyles, but they cost one less (unupped). You're not going to use their Stone Form anyway. At that point, you could just power the Eclipse with a mark of Darkness and go only Death creatures. However, since you've upgraded the Obsidian Towers, I can understand if you stick with this. Dusk Mantle is imperative to surviving, so it's only a question of speed vs. balance.