I just discovered this game a few days ago after watching TotalBiscuit's review, and I love it. I never thought I'd be able to get so into an older game. I just have a question.

I notice that when I have a lot of units summoned, especially higher-tier units, I can have 12 Manahoars and be standing next to a Manalith, and my mana recovery is extremely slow.

It also seems to be even slower if my Manahoars are feeding mana to nearby units with low mana at the same time.

Can someone clarify exactly what affects mana recovery rates?

A few things that affect mana recovery rates include the number of Manaliths you own, the number of Manahoars you own, the recovery stat of your wizard (which can be increased by accepting certain boons from certain gods), the distance you are from your closest Manalith, and any nearby units consuming mana that will need to feed off of your Manahoars (they will choose a Manalith by default if they are close to one).

Build and secure as many Manaliths as you can before engaging the enemy. In my own experience I've never needed more than three Manahoars, summoning more only if I am overloaded with souls.