I was told that there is a certain Tosafos in Bava Kamma that was written by the authors in their own blood before they were killed. Are you familiar with this and would you have a source for this?
Yes, I am familiar with this, supposedly it was regarding a Tosefos in Babba Kamma. In fact, the Lakewood Yeshiva once put out a video regarding Ahavas Hatorah and this was one of the examples. The source of this, where it is written, I don’t know.