Just had a thought from the lastest page. I remember that earlier in the chapter, someone on Disqus suggested the tank as a possible casualty of the current battle. I think this has just become more likely via two possible channels. One is that they manage to deal with the troll, but it turns out to have eaten through something vital to get inside. The other is that the troll does no damage to the tank, but whatever means are used to kill it do the damage. The second of course includes "sudden burst of magic from Reynir" scenario.
Of all the personal predictions I've had for this battle, the only one that has yet to be challenged or confirmed was "double, if not triple magic coma". Onni is out and the runes don't seem to do the energy sapping some of us have feared, so if Reynir gets one, it would have to be from something else.