|-25||This champion's AP cost for each movement is increased by 1.|
This ability is likely the most common big drawback -- champions which are lumbering usually take twice as long to get near combat and are generally easy to escape from. However lumbering champions have a significant discount and thus may end up much cheaper (for example Afflicted Corpse). Lumbering is also on champions who are designed to work from far away ((for example Treant Launcher, Glowing Slider, and Nora Beast).
Also note Lumbering is an ability and not a condition. This means if it's given temporarily, it can't be Cleansed like negative conditions would.
Lumbering stacks with other movement increases (such as those from Impeding terrain).