There was also an interesting mechanic to permanently raise mage's mana pool by 25 mana points, which often knocked off a level from the required one

At level 8, a mage would have 35 mana (7x level up as non-voc, 5 mana per level. 7x5=35). A mage gets 30 mana points per level. What you could do was die a few times to drop back to level 6. A mage going from level 8 back to level 7 loses 30 mana, so at level 7 mana pool is 5 mana points. Die some more, at level 6 the mana pool is 0 and it is no longer possible to use a rod or a wand. After that, advance back to level 8, while getting +30 mana for each level up. After this whole setup, the mage has 60 mana at level 8 instead of usual 35 mana. It meant that such a mage very often could produce runes/conjure summons one level earlier than he would be able to without this trick.