She was armed with three things.

The most trustworthy was the magecraft compass her father gave to her on her birthday. It looked like an ordinary compass from its shape and structure, but it wouldn’t point towards the north and point towards the direction where strong amounts of prana emanate out instead. Rin had experimented with it, and neither wind nor water could change the detection of small movements of prana. If something abnormal happens, this would undoubtedly be the most useful.

The rest were two piece of crystal that Rin specially crafted while she practiced jewel magecraft. She picked the two best works from her completed ones. If all the prana stored in them were to be released at once – although she’s never tried something so dangerous – it would probably cause a small explosion. It can be a weapon of self-defense in the face of danger.

- Fate/Zero: Act 8, Part 4