User blog comment:ViridianFan/A few item ideas/suggestions./@comment-1330314-20150628190815

Mana burn isn't really a good mechanic. Even against the examples you mentioned, Ryze and Karthus, either your passive does nothing against them (i.e. they have enough mana to use spells), or it completely hard-counters them (i.e. they're OOM and can't do anything to fight back until they either die or recall). I also don't really see why you would want to counter mana stacking, since unlike health or resistance stacking it doesn't make a champion tougher to fight in itself.