Talk about a mod I have been looking for. The Invasion Mod actually makes it a challenge to keep your base safe from mobs! All those tireless nights spent crafting the perfect defense to your base can now pay off! To make this mod even more awesome, there are a few different Mob types added, as well as tiers for existing mobs. You can choose different options for how and where these Mobs will spawn, so you have time to craft a good base.
This is certainly a mod to spice up your Minecraft world!