Arcane Aura provides global mana regeneration to every allied hero, so one point at level 2 or 3 gives your mid and offlane a significant mana advantage.

At level 4 allies get 2 bonus mana regen while CM gets 10, letting her cast spells very freely.

With base movement speed of 280 and a tiny HP pool, CM is a prime target for ganks, so positioning is everything.

She is a devastating early game ganker and a fight winning ultimate channeler in the mid game.

Arcane Aura quietly wins lanes across the map by fueling spell spam without CM even being there.