Servant Catalysts

During the process of summoning a Servant, the servant that is usually summoned is pretty random. While summoned servants usually tend to share similar goals and ideals with their summoner masters, it's ultimately due to the forces of randomness. It's not impossible for a summoner to summon a servant that has a completely different personality type.
To remove this risk of cosmic randomness, summoners that may be well-versed in heroic spirits and legend may try to create some sort of object that allows them to specifically summon the servant that they want. This item is known as a catalyst.
Not just any item can be a catalyst though. In fact, finding/making an item that can be used a servant catalyst can take quite some time and resources. In order for an item to be considered as a proper/potential catalyst, they must fill out the following checks that include, but aren't limited to:

• The item must be something related to the servant one is trying to summon.
• The item must have a great resemblance to the servant's related item.
• If the previous attribute can't be achieved, the item can be engraved, modified, built, etc in order to achieve the resemblance that legend tells.
• The item must be enchanted with special magical properties in order to be viewable by the Weave.
• The item can't be too vague or generic.

If all of the checks are done and the ritual is properly made, the summoner will have almost a 100% chance to summon the specific servant that they wish to have. However, even one misstep in the catalyst-making/finding process can throw off the whole process.
The following is a list of known servant catalysts that have been used to help the summoning of specific servants. Most of these were created by skilled artisans to match the descriptions of the spirits' iconic items.

• Engraved Birchwood Staff
• Engraved Silver Longsword with Bronze Pommel
• Cherrywood Musket with Goldleaf Markings
• Katana with White Wrappings and Wheel-shaped Guard
• Odachi Hilt with Purple and Gold Wrappings
• War Spear with Full-Red Metallic Covering
• Gold and Bronze Scabbard with Draconic Engravings
• Giant Bronze Halberd with Engravings
• Horn and Ivory Half-Mask