Mana Focusing is one of the 18 different Retorts available for customizing and empowering Wizards in Master of Magic.
Mana Focusing increases the amount of 
Mana generated from investment of 
Power points by 25%, and costs 1 pick. This Retort is simple and direct, but general consensus accounts it a weak choice. There are better options.
Description[]
In the world of Master of Magic, all applications of magic require expending magical energy, which must first be stored into a mystical material known as Mana Crystals. It is through these crystals that magical energy can be shaped into useable forms. Therefore, even if a wizard is capable of drawing massive amounts of energy from any source, he must still convert that raw Power into Crystals before it can be applied.
The Mana Focuser is a Wizard who has spent much of his life studying the techniques of converting raw Power into Mana Crystals, and has discovered certain ways to do so that are simply more efficient than the common methods. The Mana Focuser therefore can get more Crystals out of the same amount of raw Power, and thus create vast stores of this mystical element for later use in spellcasting. Although the Mana Focuser is not necessarily a better user of magic, the surplus energy he can store may enable him to cast spells more often, and to be able to keep many permanent spells running for a long period of time.
Effect[]
Mana Focusing is one of the advanced Retorts available in Master of Magic. It is a very straightforward Retort which increases Mana generation through investment of Magical Power - but this can have a drastic impact on the game nonetheless.
Mana Generation Ratio[]
The primary method for wizards to acquire the Mana they need for spellcasting is to generate it out of raw Power. Normally, Power is converted into Mana at a ratio of 1:1.
A wizard with Mana Focusing does the same at a "slightly" better ratio of 1:1.25. In other words, for every Power point he invests, he receives 1.25 Mana (the total Mana produced each turn is rounded down to the nearest whole number).
- For example, if a normal wizard invests
100 Power into Mana generation, he will receive 100 Mana Crystals at the start of each turn. The Mana Focusing wizard, investing the same 100 Power, would receive 125 Mana Crystals.
Mana generated or acquired through other sources (such as through Alchemy) does not receive this bonus. The bonus only applies when using Power to create Mana.
Cost and Requirements[]
The Mana Focusing Retort is only available to wizards who possess at least 4 Spellbooks in any one Realm. A wizard may have any number of spellbooks from any number of colors, so long as at least 4 of them belong to the same color.
For example, a Wizard with 
4 Spellbooks may pick the Mana Focusing Retort, and then add any number and type of other books and retorts she can afford. Conversely, a Wizard with 3, 
3 and 
3 Spellbooks may not pick this Retort, since she does not have the required 4 books in any of the Realms she chose.
When creating a new Wizard, the Mana Focusing Retort consumes only one pick.
Strategy[]
The power base is the only reasonable source of mana in the very beginning of the game, such that early spellcasting will leave very little room for research or skill improvement. You generally have work in stages, doing one of these at the expense of the others, and Mana Focusing helps if you are particularly intent on casting spells. The substitutes for the researcher and the skill practitioner are, respectively, Sage Master and Archmage.
That being said, there are more elegant ways to increase your spellcasting power. This retort is usually a poor choice and arguably the weakest of all retort and spellbook picks.
Consider that with each chosen Spellbook past the seventh in a single color, you gain a 10% increase in Research Points gained, and a 10% discount in Casting Costs, closely matching this retort's effect and granting a deeper spell selection in that color in the bargain.
If summoning units is your early goal, then the Conjurer retort is better suited to this and should be taken before Mana Focusing. Likewise for combat spellcasting, Channeler is more appropriate (though it is also considered a soft option).
Archmage is virtually always a superior choice to either Mana Focusing or Sage Master. It is a +50% multiplier, and you will almost certainly be making major investments in Spell Casting Skill at some point. From the start it gives you room to direct power away from skill, ironically, but as the game proceeds your Power in this area will be more effective than that of a Focuser in mana or a Sage in research.
Finally, with notions in mind that 
Gold is often more plentiful than Mana, that being able to swap the two is a massive convenience, and the benefit of 
Magic Weapons for your troops, consider Alchemy as a high-profile replacement for this retort.