Wherein You Explain Flask Movement Speed

Wow, so the wiki doesn't even have this mod on the item affix page yet? So out of date....

Anyway, yeah, GGG is not stupid, items will not roll mods that are literally useless for them.

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SaiyanZ wrote:

I'm guessing certain mods on a Silver Flask are useless since Onslaught is not affected by many things? eg. "Increased flask effect".

This very question was answered in the game mechanics post in the announcement section. I don't know if it's possible to get the alchemist prefix on a silver flask, but it is possible to get increased flask effect from other sources and indeed it has no effect on a silver flask. Onslaught is a boolean state and "you have onslaught" increased by 20% is still "you have onslaught".