The Hills have Ants
Just beyond the forest surrounding your brand new village, some horrible hive of Giant Ants must exist! Travelers are regularly disappeared, and the crops have been slowing dwindling after nighttime harvests by the creatures. Solve this problem, save the future of your home.
Thousands of years ago, scientists or wizards or someone experimented with size enhancement, genetic augmentation as a bioweapon, and stealth infiltration. Imagine a few ants scuttling under a door, growing to huge size, and making any soldiers in the room into more ants. Somewhere near here, this experiment must've busted out. They've since integrated themselves into the ecosystem. More recently, in the order of a week ago, some merchant carts have disappeared along with large supplies of the nearby village's food.
Queen's Chamber. Filled with 10 drones (giant ants) and the Queen (some combo of an ogre and a giant ant). She is covered in welts and bulbous sacks of fluid. If the queen is threatened, any surviving drones will swarm into the chamber to defend their queen. Also, 1d6 drones will return from the outside to assist.
Food Chamber. Inside of this room, many crates of wheat, fruits, and scattered animal carcasses. 4 drones eat here, and could likely be walked past. Inside an overturned crate is a wounded and weak merchant named Frederick. He is incapable of walking, and huddled inside this crate to avoid the ants. He hid in here when the ants attacked his merchant caravan.
Antechamber. Inside of the first room are two Ant-Men, people mid transformation into giant ants. (Stats as any weird humanoid creeps). They will shriek and click at anyone who approaches, dripping with mutagenic saliva.
Grub Chamber. Filled with squirming, torso sized Ant grubs. They could potentially be raised and treated with magic or pheromones to be your very own!
Trash Room. Piles of silver jewelry, sacks of spices, and other trade goods lay abandoned here near the entrance. The temptation is to grab the wealth and leave the village to get bled dry by these ants.. but you wouldn't. Would you?
Under Construction. This room is only half as large as the others. It is under construction, but some drones are out scavenging for more wall structures.
Weak Wall Hallway. This leads from the antechamber into the rest of the dungeon. The wall is very loosely packed dirt, and if walked past will collapse part of the ceiling on top of the party. If walking slowly past, it can be avoided. If the party collapses it, it will be rebuilt the following day by the drones.
Poison Hallway. Some of the more humanoid drones have reinforced this tunnel with branches and leaves of local plant. Their ANT transformation has made them immune to the horrible disease this plant harbors, and anyone brushing past the large leaves will need to save vs disease.
Ant Hybridization. The "saliva" of any of these monsters can be used to transform living creatures into horrible ant-hybrids. They will be drawn towards this queen, and if she is dead, they will be aimless animal creatures. Anyone who dies to these monsters will swiftly become a hybrid, progressing further each day. A cure may exist.