I am relatively new at Kassadin, trying to learn him, but I am a bit confused on when to build certain mythics. I know Everfrost is the standard, but I really don't like building it that much, I feel like I do so little damage in exchange for the active. I feel like Ludens gives me actual burst damage and I feel like a threat when I have that first item.

I am high Plat currently, and I see Fiora, Riven, and Jax with maw constantly, and not sure what I should do against them. Is riftmaker a good answer to Brusiers? fully stacked 9% bonus true damage seems pretty good, gives good health, and 16% omnivamp total when you're full build seems very good. Obviously the biggest issue is mana. I also had some questions about some legendary items. When would I build Void Staff over Rabadon's, when would I build Demonic Embrace, and when should I build Lich Bane?

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Edit: Also, according to league of graphs, the rank 1 Kassadin NA is an obvious booster who is 51-0 on Kassadin on someone else's account. https://www.op.gg/summoners/na/qwerqwerDF