Dullahans naturally have expertise with riding animals, able to ride any animal, with little to no difficulty. As dullahan are fey, animals will recognize you as a Dullahan and usually accept you using them as a mount, as they consider it an honor. As a Dullahan you gain expertise in the Animal Handing ability check. 

Your charisma score increases by 2, and another score of your choice by 1

Dullahan mature at the same rate as humans but live for around 500 years

Dullahan tend toward neutral alignments as they believe death comes equally to everybody at their own pace and also to avoid being ostracized as monsters.

Dullahan are about the same size and build as humans. Your size is Medium.

Your base walking speed is 30 feet.

Thanks to your infernal heritage, you have superior vision in dark and dim conditions. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can’t discern color in darkness, only shades of gray.

You have proficiency in the Intimidation skill.

You know Chill Touch cantrip, at Level 3, you learn the Find Steed spell, and can cast it once per long rest. Your steed counts as a Fey creature, additionally it can be stored in your shadow as an Action or retrieved as a Bonus Action. Charisma is your spellcasting modifier

You can speak, read, and write Common and Sylvan