Level up choices?

[bugmenot]

At the start of turn 10 check the message area, you'll see something like:

Your soldiers are tiring, concentration is harder, mana and rage generation are halved.

On turn 20 you'll see something like:

The battle is long, your soldiers have lost their bloodlust, you can no longer gain mana or rage.

I'm playing a mage, but don't have the concentration skill (yet), normal difficulty, I'm level about 12, but I started noticing these messages when I started making battles last longer to exploit Sacrifice.

I regain 2 mana per turn upto turn 10, then 1 mana per turn upto turn 20.
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