Orcish Fury 5e feat

The racial feat of 5e Orcish Fury is open to half-orc characters. It has copyright to Wizards of the Coast, which is available on page 75 of Xanathar’s Guide to Everything. The Prerequisite of this feat is Half-orc.

Your fury will burn tirelessly. You will gain the following advantages:

Improve your Strength or Constitution score by one, up to a maximum of twenty.

If you hit with an attack made by a simple or martial weapon, you may roll one of the weapon’s damages to add time and add it as additional damage to the weapon’s damage type. Once you use this ability, you can’t use it again until you finish a short or long rest.
Immediately after using your Relentless Endurance trait, you may use your reaction to make one weapon attack.

Is the extra damage die from Orcish Fury affected by crits?

You get 2d12 extra damage from the critical hit. 2d12[base + Orcish Fury] + 2d12[crit]

The PHB says:

Suppose the attack involves other damage dice, such as from the rogue’s Sneak Attack feature, you roll those dice twice as well.

Orcish Fury 5e’s extra damage is by definition “other damage dice,” so it applies.

You can see more evidence by comparing the wording to a sneak attack.

Sneak attack 5e says:

You may deal an extra 1d6 damage to one creature you hit with an attack

That is almost identical to the wording in Orcish Fury:

add it as extra damage of the weapon’s damage type

If a sneak attack 5e’s extra damage is doubled on a critical hit, so should the extra damage from Orcish Fury.

Jeremy Crawford seemed to support this verdict as well when he said:

Suppose you score a critical hit. You can roll all of the attack’s damage dice again. It does not matter regarding the source of the dice.

Jeremy Crawford has recently given a direct ruling for this which agrees with all of the above:

Suppose you score a critical hit. In that particular scenario, you will get to roll the attack’s damage dice an additional time. Suppose the attack requires extra dice from a point like Orcish Fury or Sneak Attack. You also roll those an additional time.