Originally Posted by Phreak
Here's what it is:
The orb deals magic damage on the way out
The orb deals true damage on the way back
True damage is unaffected by "% damage increase" such as the masteries Havoc and Executioner. It also does not benefit from bringing things into negative MR, while magic damage does.
Thus, sometimes magic damage will actually deal more damage to a source than true damage will, which is why you're seeing the way out occasionally deal more damage than on the way back.
I just wanted to clarify, does this mean Ignite doesnt increase on damage by effects such as Poppy's ultimate, and Swain's E, and Vlad's ult? I was always under the impression that it did.