Battle Mana Value Incorrect
During a game, my opponent had a "Defiant Thundermaw" (back side of Invasion of Tarkir) and 2 voldaren epicure in play. I cast a Riveteers Charm with the mode "Target opponent sacrifices a creature or planeswalker they control with the highest mana value among creatures or planeswalkers they control."
Based on this rule: 202.3b The mana value of a transforming double-faced permanent or spell’s back face is calculated as though it had the mana cost of its front face.
The back side of Invasion of Tarkir should have a mana value of 2 (based on the front side), however it must be calculating as zero, as my opponent was able to sacrifice one of the 1 cmc epicures instead, and this lost me the game.
Unfortunately I did not capture a screenshot, however I am going to upload my log file if that is helpful.