I just wanted to record what works well for me. I haven't played enough to get too in depth with matchups, if anyone is to follow this build, it's meant to bully bot lane with magic pen. Usually magic resist isn't taken by adc's and supports and brand has the potential to apply a lot of magic damage, so I prioritize flat pen. A typical adc mr at level 18 (without building it) is still less than 40. That is why this build rushes morellonomicon instead of liandry's, because 33 magic pen, which is close to true damage, hurts. In my experience the threat of suddenly taking away chunks of the enemy's health bar is more threatening than burning them. So long as you are somewhat even or ahead and your adc isn't playing too passive, you should be able to harass the opposing adc aggressively. Now, mana. Making the most of manaflow band, which is to wait for its cooldown, is optimal for not running out of mana. I just find that a decent rate of expenditure. Once manaflow band reaches its maximum, and you've upgraded your spellthief's at least once, you should be good on mana. It will run out in prolonged fights, but its usually plenty for at least 1 and sometimes 2 teamfights in a row.