Master Rank

Overview
Master rank is simply the abstraction of your mage's ability to sustain a servant. It incorperates the amount of ciruits you have, the skill and training as a mage, how long your family history is (and if you have a crest or not). and other such things. It influences what rank your servants stats will become once it is summoned.

There are four Master Ranks.

Extended
A master of this level is considered the prime choice by the grail, it is someone with both intent to use the grail, and someone who possesses a great amount of mana and circuitry. Basically it will be someone who is a great magus of some standing.

Servants with an Extended master can utilize their noble phantasms as Cherubim rank masters, as does Caster's magic. Skills and stats get 3 extra points each that cannot be stacked more then 1+1.

Cherubim
A master of this level is considered the secondary choice by the grail, it is someone with both intent to use the grail, and someone who possesses a above average of mana and circuitry. Someone who is from a famous family for example. (Canon example is Rin)

Servants with a Cherubim master can utilize their noble phantasms freely up to 4 times a day. Caster's can use magic at any rank. Skills and Stats are granted 2 extra points to put wherever they want. This is the maximum rank a player can start with.

Throne
A master of this level is considered the basically the last choice the grail will make, it is someone with both intent to use the grail, and someone who possesses an average amount of mana and circuitry. Someone who is a thaught mage but not much more.

Servants with a Throne master can use their noble phantasms up to B rank twice a day, Caster's cannot use magic above B rank, skills and stats are unaffected, this is the average.

Dominion
A master of this level is only considered by the grail to fill a void in the selection slots, it is someone with either / or both intent to use the grail, and someone who possesses at least average of mana and circuitry. someone who is basically unaware or untrained as a mage.. (Canon example is Shirou)

Servants with a Dominion master can use Noble Phantasms of C rank once a day or lower ranks twice a day, Caster's cannot use magic above C rank, Skills are pulled down to rank C.