Tiefling

As an altered race, Tieflings mostly stay true to their descriptions provided in the source books of 5e. The Players Handbook tells you all you need to know about the way they act, and how societies react to them. However, a few notable differences are as follows:

Demonic Influence:
Tiefling can be grafted onto any racial template you want. You can play a Human Tiefling, a Goliath Tiefling, a blooming Gnome Tiefling if you so wish. The stats all stay the same and you gain no benefit from this choice, its just aesthetic. The only races unable to be used with a Tiefling graft are ones like Duergar, or Deep Gnomes; already unique renditions of an established race. Tiefling grafts also cannot be used on a race of 'alien' rarity.

Hellspawn:
When a soul has spent enough time in a respective afterlife, or a celestial / fiend are killed, the soul is sent back to the Prime Material to be reincarnated into a new form. More times than not, these reincarnations bear no resemblance and no effect of the lives before it. A man could be the reincarnation of several fiends and never stray from a path of good, or have any indications of his souls past.

However - very rarely, the soul of a recently slain fiend is filled with such malicious, hellish energies that it manifests in its new reincarnation. The influence tends to end there, however sometimes visions of their past life, strange pulls toward evil, and abyssal tendencies present themselves in Tieflings.

Infernal Refuge:
With the knowledge that they were past fiends, many people do not take kindly to Tieflings being born. Most religious authorities simply 'euthanize' the children, some send them to a 'refuge', and fewer still allow the baby to be kept by its parents.

The 'refuge' is a Tiefling colony of the coast of Rai'Kor - there many Tiefling live quite happily away from the main lands of civilisation.