Rnager: Vermin Lord (Homebrew: Grim Hollow)

Vermin Lords cultivate loyal hordes of disease-bearing rodents to help them in their efforts to stem a greater evil. For many of these rangers, that greater evil is some kind of societal ill, but a rare few see their fellow humanoids as an infestation that threatens the natural world. Regardless of their goal, they make their homes in sewers, slums, and other forgotten places, where they are free to plot against their enemies and tend to their vermin kin.

Vermin Lord Magic

Starting at 3rd level, you learn an additional spell when you reach certain levels in this class, as shown in the Vermin Lord Spells table. The spell counts as a ranger spell for you, but it doesn’t count against the number of ranger spells you know.

Verminkin

At 3rd level, you can comprehend and verbally communicate with vermin (mice, rats, and other rodents determined by your DM).
Additionally, you can use an action and expend a spell slot to summon rodent hordes. When you do, you summon a number of swarms of vermin equal to twice the level of spell slot expended. Each swarm is summoned to a space you can see within 30 feet.
Swarms summoned in this way go on your initiative, starting on your next turn. These swarms obey your verbal commands (no action required by you), defending themselves by taking the Dodge action if you do not give them a command. Your vermin swarms flee the area and disperse after 10 minutes or when you use this feature to summon other swarms of vermin.

Septic Strikes

At 3rd level, you leave a septic filth behind to fester in the wounds caused by your and your verminkin’s attacks. As a bonus action, you can choose any number of creatures within 60 feet of you that took damage from a weapon attack made by you or your swarm of vermin this turn. Chosen creatures take 1d4 necrotic damage.

Filth and Fortitude

By 7th level, the time you’ve spent with plaguebearing rodents has rendered you immune to disease. Additionally, you gain proficiency with Constitution saving throws.

Infectious Spread

At 11th level, when you use your bonus action to deal the damage granted by your Septic Strikes feature, each creature that takes damage must make a Constitution saving throw with a DC equal to your ranger spell save DC. On a failure, the creature becomes poisoned until the start of your next turn.
You can use this feature a number of times equal to your Wisdom modifier (minimum once). You regain all expended uses of this feature when you finish a long rest.

Strength of the Swarm

At 15th level, while you have a swarm of vermin summoned with your Verminkin feature, you can call on your rodent minions for defense. When you take damage while one or more of your swarms of rats are within 5 feet, you can use your reaction and choose one of those swarms to take the damage instead.