Serum Fury

Barbarians of this subclass take advantage of not rage, but alchemy, injecting strength-enhancing solutions into their bodies.

Inject

3rd level: Inject: As a bonus action, you can expend a dose to inject your body with a mixture of chemicals that increases your physical prowess for one minute, but you suffer a random after effect for the following minute after using a dose. The amount of chemical doses you have increases by one every level, starting at 3 at 3rd level. When you inject a dose, you choose one of three effects: gain 1d4 temporary hp, double your damage for the duration, or double your running speed and jump height. You regain all used doses after a long rest, or you can use an alchemy kit to make more.

Roll a d20 to determine the after effect of the injection. The after effects are as follows: On a 1 you fall unconscious, on a 2 or 3 you become poisoned, on a 4 or 5 you become blinded on a 6 or 7 your damaged is halved, on a 8 or 9 you attack a random creature within range , on a 10 or 11 disadvantage on next attack roll, on a 12 or 13 disadvantage on next ability check, on an 14 or 15 you become deafened, on a 16 or 17 speed is halved, on a 18 or 19 you fall prone, on a 20 you suffer no after effect

Toughened Bloodstream

At 6th level you may use multiple doses of any type of injection, other than double damage, and you may use multiple different types of injection at once, using that number of doses each time. You also gain immunity to disease, and the ability to reroll an after effect once per short rest.

New Mixtures

At 10th Level you may select three new injections from the ones listed:

Restorative Fluid: You may end one negative status condition afflicting you.

Precision Serum: You have advantage on attack rolls for the duration.

Toughener: Attack rolls against you have disadvantage for the duration.

Fury Mixture: You get an extra attack for the duration.

Augmenter

At 10th level you gain one of three advantages: Underwater breathing and a swimming speed equal to your walking speed, a dragonborn breath weapon, or daggerlike claws and a climbing speed equal to your walking speed.

Serum Lord

At 14th level you suffer no ill after effects from taking doses, and are resistant to poison damage and immune to being poisoned. In addition, when you drop to 0 hit points, you can, as a reaction, use all of your remaining doses all at once. As a result of this, you gain the bonuses of all of the injections you picked, as well as advantage on strength and constitution checks, an increase to one size up for 30 seconds, and immunity to all damage, 2 rounds. Afterwards, you suffer one level of exhaustion, and can’t use this again until after 1d4 long rests.