Log 15 Blood and its Sympathetic Links
If I can think of more examples before I die and how I think they work then I will include those. Just so you know this log has many conjectures based on examples with very little science, I can't say if these are facts as I can't test to know for certain however.
Beast contracts
Blood is used on a special scroll filled with a space-time jutsu. This blood is a link to a person's body that allows summoning to their location or to summon themselves to the linked land of contracted beasts.
This is nearly identical to how the thunder god mark works. Only the thunder god mark requires one to set up and determine the destination oneself.
For the scroll however, one uses chakra to allow physical movement through this bridge with the use of a Jutsu and the contract as an intermediary to specify the coordinate for the summoning.
All that the scroll does is become a link between two separate seals. Blood is the essence of the Yang, the physical body that anchors a person to the physical world. This is used as a medium to connect themselves to this bridge.
Edo Tensei
Blood is the material required for Edo Tensei. Blood acts as an anchor while chakra is the connection between the energies of the body and soul.
Through the sacrifice of a person's life, they are sent to the pure lands and through that connection to the pure lands. The blood is used with the chakra acting as a bridge from the body to the soul to call upon it from the other side.
Now that the spirit is summoned it is bound in a body made of yang energy created from the life force of the sacrifice and not real flesh and blood. It allows the body to heal, to never bleed, and to quickly produce chakra as the strong soul summoned can convert all the excess physical energy to create more chakra for Jutsus.
Jashaun Blood rituals
The blood of a target is extracted and exposed to a ritual to cause an effect. The most known of these is the Death Controlling Possessed Blood technique.
This technique is similar to the Shadow imitation technique but instead of connecting one's spiritual energy to another Yang energy and manipulating their bodies through the medium of shadow yin release.
In this technique, you use the medium of the blood taken from the victim and make it a part of one's own Yang energy by ingesting it. Through the use of a symbol, intent, and chakra, I will go more in-depth about this when I write about Fuinjutsu. They create a link between the body that has a part of the victim's blood and the body of the victim through the use of the link between body and soul that chakra possesses.
Now that this link exists one can cause physical damage on one side of the ritual and the same damage Is linked to the other side.
Footnotes:
In the next log, I will go back to a topic I slightly skimmed back in log 9. I skimmed over the idea of thermobaric explosives so now I am going to go in-depth on these principles and how we might be able to use these principles in fire release.