What if the rift herald could become a 6th temporary teammate ?
Like you defeat him so then you have earned his honor in helping you ? to do one specific task like the mark of void becomes this global kindred passive but instead YOU choose who / what to curse with the "mark of the void".
So i defeat him
Okay i want tier 2 tower ?.. MARKED
Go solo dragon ? sure why not were pals after all.. MARKED
Go assassinate 
bot ? ok.. MARKED
It would be hilarious sending the rift down mid to kill someone or destroy a tower by himself honestly i can see it. Then if he finishes his task or gets destroyed he returns to the void.
