Blood Skull Gu

Blood Skull Gu belongs to the Blood Realm, and is a very dangerous Gu. The danger doesn't imply that it got an attack ability that one would rather not be against, but because it uses the blood of relatives to increase the user's aptitude. This ability is very rare that only few Gu can increase the amount of Primeval Essence stored in Aperture.

Appearance
This Gu is a crystal with red stripes that is shaped and sized like the skull of a kid that can be held in a palm. Where the eye sockets are localised there appear to be glowing purplw flames.

Ability
Gu Worms' ability is to increase the Gu Master's aptitude as long it can absorb the blood of the family members of the Gu Master's or the same bloodline as the latter's. This ability can even grant the the Gu Master one of the Ten Extreme Physiques.

Once 100 blood related members Blood Skull Gu would have had reach its limit, turning completely blood red. Once this happens the Gu Master will raise the Gu over their head, and at this moment the skull's mouth will open to let out a fragrant stream of blood to pour forth and  drenck the Gu Master's aptitude by 10%.

This Gu also raises its rank to have stronger effects and by killing more clansmen the more will the the aptitude increase, even being effectine for Gu Immortal s.

Drawback
To increase the aptitude of just a person requires the Gu to absorb a high volume of sacrifices and the only way to go around it would be to kill a clansmen who possesses an extreme physique and reach the limit of A grade talent from having ordinary talent, meaning C grade talent. The version at rank 5 reduces the number to 1 to reach A grade aptitufe, but it requires the same number as its rank 4 counterpart to increase the aperture's limit by 10% to reach 99% (peak A grade talent). Once it reaches the Immortal rank it keeps the ability of the mortal version, but becoming strong enough to affect the immortals. As its ability grew to this extent the sacrifices required increased to affect immortals, especially when the immortal's rank progresses, also needing the sacrifice of a blood relative who is also an immortal.