...and Adder proves he's never been on a burns ward...
If you want a character to be mobile, then rely on psychological 'persuasion'. If he's so burned there's raw skin and blisters over his body, he'll lose the ability to properly thermoregulate, his organs will fail and he'll die - if infection doesn't set in first and he dies of blood poisoning. That's why burns victims have to go to hospital, yaknow?