Mummies can be found inside caves and tombs, being in this last place where they can revive to attack the player. But beware, the mummies also can come to life and attack you while you have them in your inventory. With 20 toughness they can be a bit risky to carry especially if you have more than one. This event only appears at night during resting/camping in the open and having a mummy in the inventory also can initiate an argument with the natives, who will require the player to return the mummy to them. For all this, it is highly recommended that the mummies should be the items with the high priority for being stored in the stash of missions and polar stations.