[[Sister Laurel, do Catholic Hermits seal their vows with blood? I've heard of blood vows (something about the Mafia) and blood oaths but before today I never heard of a Catholic hermit sealing his or her vows with blood or a Catholic priest allowing it. Is this part of canon 603 or the ritual of consecration?]]
Assuming this is a question prompted by an actual situation and not by an old (or new!) Sister Fidelma mystery, I should say that the entire situation you describe completely creeps me out. However it also raises the serious question of the use of normative rites for profession.
One of the things I don't think I have written much about here is the idea that public professions and consecrations are done according to approved rites and liturgies. This, I think, is part of the truth of the traditional saying "as we pray, so we believe" ("Lex orandi, lex credendi"). Let me also say that it goes almost without saying that the approved rites for religious profession in the Roman Catholic Church (including the profession and consecration of the c 603 hermit) or the consecration of Virgins do not EVER use blood to seal the commitment.
The idea of doing so smacks of pagan sacrificial or esoteric rites which attribute mystical powers to blood or think in terms of a kind of crude physicalism and magic. (This is the kind of mistaken and unsound physicalism that talks about hosts spurting blood or speaks of munching on Jesus' bones or fingernails when one is consuming the Eucharist! Too often have Catholics been accused of believing such nonsense. Too often have theologically or spiritually naive Catholics contributed to this judgment --- something which has needlessly inflamed anti-Catholic sentiment over the centuries.) In any case, this notion of sealing vows in blood certainly ignores the fact that Jesus' death and resurrection, something celebrated anew in the Mass that contextualizes a public profession, has done away with such things forever.
Contrary to what you describe or at least imply has occurred, I honestly can't imagine a Catholic priest allowing such a thing either --- and of course in the profession and consecration of diocesan hermits we are also dealing with diocesan bishops and canonists who absolutely would never allow such a thing to happen. As alluded to above, hermits in such situations are ordinarily professed using either the established Rite of Religious Profession approved by the Vatican or a version of profession for anchorites which is vetted by the hermit's Diocese beforehand. Whichever is used, the insigniae given, the vow formula and forms to be signed and witnessed, and the liturgy more generally are all approved beforehand. (Any individual accommodations are prepared and submitted to the diocese prior to the day of celebration.) The necessary forms are embossed or stamped with the diocesan seal and signed by the Bishop, the Ecclesiastical notary and/or Vicar for Religious, the one professed, and witnesses (pastor, delegate, etc). Barring an inadvertent paper cut or something similar blood plays no part at all.
While all of this may seem to be nit-picky and legalistic it really does serve the foundational truth of "Lex orandi, lex credendi." We Catholics do not make blood oaths and no Catholic Hermit professed by the Church to live eremitical life in her name uses such a gesture with her vow formula because it does not comport with our faith. Could you please let me know where you heard of or read about such a thing? I am actually feeling a bit stunned or off-footed by the question; the notion that anyone might do such a thing, especially a Catholic hermit in a Roman Catholic liturgy is offensive.
I admit the profession ceremony was intimately holy, beyond anything I could ever have dreamt nor asked for. God provides! I yet have the vows written, signed by the priest and myself, my blood spread inside a small heart drawn at the bottom--a seal that only my spiritual father has seen. (cf.,Major Occurrence)