Bleed for this. If you’re an HBO Game of Thrones fan, you know the medieval show returns for one more round of intrigue, mayhem, blood, and etc. on April 14. Out at South by Southwest, HBO has staged another mind-popping activation, this time to celebrate the end of the series. The multimedia/real world extravaganza has 80 actors, a full choir, interactive experiences and, yes, blood donation. Can’t make it to SXSW? Experience it through me.