Rift Mage: weaken

Now this is not about the shocked bug, read a lot about that. I must not understand how the passive ability right under Veilstrike works. Enemy is weakened with an upgrades stonefist, then i toss an imolate or something and mana is not refunded. If it matters, i also have the passive right under winter something, the one that freezes the enemy. Mana for standing still. Would those 2 bug eachother?

How is this passive supposed to work?