My wife and I used to have a whole pack of cute, adorable rats. They were sweet, they were lovable and we were heartbroken when their rodent lives came to their inevitable end. What better way to honor them than to create a rat-inspired monster for your adventurers to slay?
The Plague Rat isn’t strong on its own, but it comes with a skill that lets it capitalize on rats’ biggest strength: numbers. A clever and patient GM can build up an entire horde of rats that are the perfect tool to overwhelm overconfident PCs.
Tiny beast, unaligned
Armor Class 10
Hit Points 1 (1d4 – 1)
Speed 40 ft.
STR 2 (-4) DEX 14 (+2) CON 8 (-1) INT 10 (+0) WIS 12 (+1) CHA 4 (-3)
Senses Darkvision 30 ft., Passive Perception 11
Challenge 0 (10 XP)
Keen Senses. The Plague Rat has advantage on Wisdom (Perception) checks that rely on smell.
Infectious Recruitment. Once a day, a Plague Rat can venture out and search for other rats to infect. Each time it does this, four hours of in-game time pass. The GM should roll one 1d6 for each hour. They should then tally up the dice results and an add an equal number of new Plague Rats to their number. The GM should recruit no more than a 10,000 Plague Rats at a time.
Find an Entrance. An individual Plague Rat can use its keen senses (Perception DC 16) to find an entry point into a structure. The GM can award advantage and disadvantage at their discretion based on the structure being infiltrated. If the PCs make an attempt to barricade or secure the building, the Perception DC should be raised to 18. The GM can reduce the required DC by having a Swarm of Plague Rats gnaw on the barriers to weaken them. The GM can award the infiltrating Plague Rat a +1 bonus to its Perception DC for every 10 minutes of ingame time that the assigned Swarm weakens the PC’s barriers.
Once a Plague Rat has made it inside a building, the GM should perform an competitive Stealth DC with any nearby player characters to remain hidden.
Form a Swarm. If the GM has 20 Plague Rats in play, they can be combined into a Swarm of Plague Rats. Break extra rats into additional swarms of 20 with the following stats:
Armor Class 10
Hit Points 20
Speed 40 ft.
STR 14 (+2) DEX 10 (+0) CON 8 (-1) INT 10 (+0) WIS 12 (+1) CHA 2 (-4)
Damage Resistances Bludgeoning, piercing, slashing
Challenge 1/4 (50 XP)
Swarm. The swarm can occupy another creature’s space and vice versa, and the swarm can move through any opening large enough for a Tiny Plague Rat. The swarm can’t regain hit points or gain temporary hit points.
Diseased Bite (Lone Rat). Melee Weapon. Attack: +0 to hit, reach 5ft., one target. Hit: 1d4 piercing damage. If the Diseased Bite deals its maximum 4 damage, its target will contract Turb Mortuu disease. While the Plague Rat strain cannot control non-rodents the same way it does its namesake hosts, infected PCs will serve as beacons for the disease’s hive mind. Any Plague Rats in the area will be able to track them until they’re cured of the disease.
Diseased Bite (Swarm). Melee Weapon. Attack: +0 to hit, reach 5ft., one target. Hit: 3d6.piercing damage. If any dice deals its maximum 6 damage, its target will contract Turb Mortuu disease.