Little does he know Riven counter's Yas and I am a very good Riven which means he's going to have a very bad time. which means he's going to get very mad when this continues to happen.
Actually if you read the lore the Runic Blade she wields is supposedly very heavy, especially in comparison to other more common heavy weaponry the Noxus army wields. It is also supposed to dwarf her in height, as you can see from her ult. Which, for some reason, is why she appreciates the blade so much. She smashed it after witnessing Singed's genocides.
On topic, I guess it could be light after she smashed it, but originally she liked it due to it's weight.
