These crossbreeds tend to mature at the same rate and age as tieflings, but will live as long as 200 years. 

Half E/T are nearly always chaotic, either it be for the good of others and betterment of themselves. Whilst its possible for them to be not chaotic, their harsh upbringing and mixed races will certainly affect them and bring them closer to chaos. 

Half-elves are about the same size as humans, ranging from 5 to 6 feet tall. Your size is Medium.

Your base walking speed 30ft. However, you may have the option to fly if you are born with wings.

Thanks to your elf an tiefling blood, 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 advantage on saving throws against being charmed, and magic can’t put you to sleep.

You can read, write and speak in common, elvish and Infernal.

Your are proficient in two skills of your choice.

You have resistance to fire damage.

You know the thaumaturgy  and  detect magic cantrip. When you reach 3rd level, you can cast the hellish rebuke and faerie fire   spell as a 2nd-level spell once with this trait and regain the ability to do so when you finish a long rest. When you reach 5th level, you can cast the darkness spell once with this trait and regain the ability to do so when you finish a long rest. Charisma is your spellcasting ability for these spells.

If you have grown wings from your tiefling parents genes, you may use them to fly the same distance as your movement speed. They take the look of either infernal/fiend wings or bat wings. These wings can be used instead of your walking speed(cant use both) and you cannot fly higher that 5ft. 

Your charisma increases by 3 and another ability score increases by 1, but another decreases by 1