Originally Posted by Maligan
But that doesn't make any sense...
Name one other such non-channeled DoT debuff in the game that dynamically changes damage after being applied.
This isn't a channeled spell like Fiddlesticks' Drain.
It's a singular debuff that's applied to an enemy target.
If it's applied while the enemy is movement impaired, it'll do more damage for the entire duration of the debuff.
If it's applied while the enemy is NOT movement impaired, it'll do less for the entire duration.
It can't change suddenly after being applied.
If you don't believe me, test it yourself.
I'm just reporting what I saw when I tested it.
The only debuff that depends on the state of the target is Viktor's Gravity Field, which requires the target to already be slowed to build another stack up to ultimately getting stunned. That's why Yi, say, can run through without getting stunned. Apart from that, there are plenty of debuff effects that decay or build over time, like Lulu's Glitterlance and Trundle's Agony. So dynamic debuffs definitely exist, and debuffs that have to check for the target's current state also exist.
On the other hand, we don't have any previous examples of a DOT that does double damage under some condition at all. So why be surprised that the first one that gets revealed has a dynamic component? Isn't that better and more intuitive given that the description says "if their movement is impaired, they take double damage from this effect" and not "if they're movement-impaired on cast, they will take double damage for the full duration"?
I think that you're imagining two versions of the debuff - a double strength one and a normal one. What's actually the case is that there's only one version that checks for the movement-impaired condition for each tick of damage.