This could've possibly been Sirius Black's best yet worst idea he's ever had, and executed fully. Leaving 6th year midway was a no brainer when it came to him, for in no universe would Sirius Black ever sit and watch the world crumble. Sirius came from a family of dark wizards, and he rather lay down his life than watch them take over the world he loves. Tho a group of underage 16 year old wizards traveling the muggle world would've brought too much unwanted attention, thus Howler. Also on ao3 @ slytherinlex