Blood is the aspect of relationships and commitment, both on a personal level and a societal level. it’s about how people bond together and rally under a common banner/ideology. its also about attachment to physical circumstances (being rooted in the laws of outside society is important for an aspect focused on how societies collectively function).
As @theworstpersonintheworld eventually convinced me of, Its also about violence. Not just in physical terms (tho i can see it manifesting that way–the Red Miles are an explicit Blood symbol that emerge from the symbol of a monarch’s Rule over a people) but as the “removal of choice”, as Mike Rugnetta describes it.
In other words, the violence we all subject ourselves to in order to be part of society-everyone gives up SOME degree of freedom in order to enable the collective functioning of the whole.
For example, traditional marriage tends to come with an expectation of exclusivity or at least sticking by your partner even when its not convenient-its a sacrifice of the “freedom” to always look out for yourself, because you’re now bound to another. Marriage is a societal institution and a form of close partnership, so it parses in connection to Blood.
Heart concerns the soul, expression of self, and identity. its symbols are identifiers of unique personhood–nepeta’s blue cat hat, dave’s sunglasses, hats in general as signposts for an individuals’ “Identity”, whether that identity relates to work or interests.
It also relates to romance, but rather than commitment and companionship it focuses on passion and the deep inner urge towards togetherness that comes with Love. It’s concerned with soulmates in the existential sense, relationships as a means of two souls expressing the desire to Be Together.
Hopefully this helps?
Flying through Storytelling 