"I summon thy body to come to my side, and throw my fate unto thy sword. By the Holy Grail, tonight answer my summons if thou dost abide by my call. This is my pledge: I shall become all the good of eternity. I shall spread all the evil of eternity. Thou, defender of the three spells, come forth from the binding circle, custodian of the balance!"
"What is thy bid- You are not my master."
Shinji spun to face the voice that had interrupted the summoning ritual's script. "What?!"
The Servant that had snuck up on him was tall, at least to Japanese eyes, and powerfully built, and was giving the violet-haired boy the sort of look most people reserved for the unidentifiable something found in the refridgerator behind the coleslaw on coming home after a week-long power outage. "You may have spoken the words, but they're not the part that matters. Where is she?"
"I am your master!" the boy shrieked back, waving the tome that held his spells. "I command you to-yah!" He flinched as the Servant seemed to vanish from where he had been standing and reappear only inches away with a tap of sandal on floor and a sharp flutter from his long, swirling green coat.
One hand flicked out and waved a spiral of brilliant blue lines through book just as they collapsed down into a single point and exploded forwards in a fierce jet, and the other wrapped literally iron fingers through Shinji's lapels and yanked him up to eye level. "If you make me ask again, I'll stop being gentle. Where is my Master?"
...Scarily enough, this actually fits really well. I usually can't see him going anyplace without being overpowering, but...
Ja, -n
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"Puripuri puripuri... Bang!"