Talk:Deathfire Touch (Season 2016 Mastery)/@comment-27719318-20160202024000/@comment-26071360-20160203152355

Deathfire Touch is applied once with the ratio you said per time the ability ticks, subsequent ticks refreshing the duration. So in the case of Malzahar's E, Deathfire Touch is applied and reapplied every 0.5 seconds (keep in mind the duration of the debuff does not stack). So it looks something like this, every | representing 0.5 seconds.

Cast | 10+DT | 10+DT | 10+DT | 10+DT | 10+DT | 10+DT | 10+DT | 10+DT

So all in all, E would apply Deathfire Touch for 4.5 seconds total, assuming I'm managing to calculate this correctly. Either way, the important part is that the ability is reapplied with every tick of a dot, which is why DoT mages like it especially. Think Brand hitting multiple people with his W, applying his Blaze passive and Deathfire Touch to several targets without the downside of the AoE reduction that champions like Ziggs would have to deal with.