The Bug Swarm

 In this biome you can find many monsters like:

Swarm Roach: a basic fighter bug that will become faster when you hit it.

 Vile Roach: slightly tougher reskin of Swarm Roach that poisons you.

Brute Roach: unlike the others it has a unique model and not only gets speed upon being hit but also gets resistance and is the toughest of the three

 Strider: A bug that is taller than the player and is pretty basic and does not do anything special.

Worker: a small passive bug that explodes upon death but rewards you with a food sack that can be cooked.

Another biome in the mod is the infested desert.

The mobs that spawn here are:

Volcanibug: a fiery bug that, upon death calls down a lighting strike.

Fire Roach: a Roach variant that sets you on fire.

The mod also adds one boss: The Roach Lord.

Every time the Roach Lord is hit, he spawns a roach. most of the time it will be a Swarm Roach but it can also be other roaches as well.

Upon death he drops the roach staff and infested transport which is used to ignite the portal to the new dimension.

Roach Staff: a staff that spawns friendly roaches that attacks mobs when you hit something with it.

Disgusting Bait: Used to spawn the Roach Lord

Rotten Sword: weak sword that is uesed to craft a sword better than diamond!

Unrotted Sword: a sword slighlty better than diamond which can be used to craft the very expensive Vile Blade!

The Vile Blade: An extremely powerful weapon that poisons enemies! 

Corrupted Spine: essential material.

The new dimension is called the infested planet. it is perma-dark and generates like the overworld but with only the biomes this mod adds. the portal is made using the portal blocks. it is ignited using the infested transporter.