Being selected by the Holy Grail as a Master allows you to Summon and to a certain extent command a servant, however before you begin it is important to understand the power and option given by the Grail. The command Seal that has apeared on you is divided into three pieces and acts as the right to fight in the Grail war, so long as you posses it you are eligible to win the Holy Grail War and can command your servant. However not all servants have the same beliefs and alignments and as such there may be times in which you must force a command. It is possible to force a servant to do anything up to three times, one for each part of the command seal however for each forced command used, a part disapears and if all three disappear your status as a participant and ability to command your Servant disappears with it. It is also possible to reinforce your Servant with the use of a command seal. In addition the command seals can be removed physically by severing it off of its users body or through mystic means so be careful.
The decision you must make as a master is how you wish to summon a Servant. There are two ways, through catalyst or through the Grails will. By default the Servant summoned is based on who the Grail believes your best partner is, however not all servants are equal in all measures and if there is a desire for a single Servant or Group of Servants, it is possible to use an artifact that relates to the spirits in question in order to force a related Servant to apear in place of the one chosen by the Grail. Remember however that not all Servants will like the way you think and that compatibility is the Grails main considerations when selecting a servant when no catalyst is used.
