Your ability scores each increase by 1. Or you can give one ability score +2

Monstrous Traits

When you assume your abominable form, you choose three traits from the list below. These traits reflect the grotesque adaptations of your body and grant you unnatural abilities. Unless otherwise noted, a trait can only be chosen once.

Monster Senses

You enhance one of your senses—smell, hearing, touch, or taste. You have advantage on ability checks that rely on this sense. The sensory organs for this sense manifest across your body in a grotesque fashion.

Monster Mutations

You develop an unnatural appendage or prominent physical mutation in the shape of a hand or a tail. You can use your bonus action to make a second weapon attack without adding your proficiency to the damage using the appendage. 

Monster Enhancement

You gain resistance to one of the following damage types: lightning, cold, fire, poison, thunder, or psychic.

Monster Hide

Your skin thickens into a leathery or hardened hide. While you are not wearing heavy armor, your AC increases by 1.

Monster Strength

Your muscles swell to unnatural proportions. You have advantage on Strength saving throws, and your carrying capacity is doubled.

Monster Sprint

Your body adapts for speed. Your base walking speed increases to 40 feet.

Monster Liquid

Your body becomes partially amorphous. Once per long rest, you can reshape yourself into a convincing disguise of your choice, appearing as another creature. A creature that inspects you can discern your true nature with a successful DC 16 Wisdom (Perception) check.

Monster Environment

Your body adapts to survive hostile environments. Choose one environment or region too dangerous for normal humanoid life. You are immune to all harmful effects of that environment (such as extreme cold in a frozen wasteland, or poisonous air in a volcanic cavern).

Monster Shrinking

Once per long rest, you can reduce yourself to a Tiny form for up to 1 minute. While in this form, you can squeeze through spaces as narrow as a crack in a door. You return to your normal size when the effect ends or when you end it as a bonus action.

Monster Claws

You sprout hooked claws, a malformed horn, a stinger, or a similar natural weapon. When you hit with an unarmed strike using this body part, you deal an extra 1d4 damage of the strike’s type.

Monster Poison

Your body produces venom. When you hit a creature with an unarmed strike using a natural weapon (such as claws, fangs, or a stinger), the attack deals an additional 1d6 poison damage.

Monster Endurance

You are tireless. You are immune to magical or mundane effects that would cause you to fall asleep, and you don’t suffer exhaustion from prolonged physical activity.

Monster Insomnia

A portion of your brain and an extra set of eyes remain alert while you rest. During a long rest, you remain aware of your immediate surroundings and can spot nearby danger.

Monster Hypnosis

Your body manifests unsettling patterns or mesmerizing colors. You have advantage on Charisma (Performance) and Charisma (Persuasion) checks made to influence creatures who can see you.

Monster Voice

You learn to speak with a monstrous lineage. Choose a type of creature (such as abominations, monstrosities, or vampires). You can communicate with creatures of that type, even if they lack a mouth or spoken language.

Monster Vision

You develop additional eyes or strange sensory organs. Choose one of the following:

• Blindsight (10 feet)

• Tremorsense (10 feet)

• Darkvision (60 feet, or extended by 60 feet if you already have it)

Monster Lineage

You have a deep, instinctive connection to a monstrous lineage. You can ask your DM one question about your chosen monster type. The DM must answer truthfully and with information you would reasonably know due to your lineage.

Monster Trait

Instead of choosing one of the listed traits, you and your DM may agree upon a custom monstrous trait that reflects your abominable form.

Abominations reach adulthood in their late teens and live for around a century. 

Abominations vary widely in height and build, from barely 5 feet to well over 6 feet tall. Regardless of your position in that range, your size is Medium or small.

Your base walking speed is 30 feet.

You can speak, read, and write Common and one extra language of your choice. Abominations typically learn the languages of other peoples they deal with, including obscure dialects. They are fond of sprinkling their speech with words borrowed from other tongues: Orc curses, Elvish musical expressions, Dwarvish military phrases, and so on.