Classic examples of arcane links are hair, blood, spit or fingernails. To be a viable link, the sample must be well preserved and undiluted, though not necessarily fresh. Other arcane links include a spellcaster's talisman, as well as totem bound objects.
With the proper arcane link, spells that normally require line of sight, can instead be cast from miles away. A Creature's true Name can also be used as an arcane link.
With a good arcane link, you can cast sight range spells at a distance of 1 mile per level of your sphere.
If a creatures true name is used in a spell, that creature is more likely to be affected strongly by the spell. Targets are affected in one of the following ways...
If the target gets a defense test it is halved.
If the target has magic resistance against the spell it is halved.
Effects on beneficial spells are somewhat more limited, but might include a slightly longer duration, at the discretion of the GM.
Most peasantry, unless they have had some experience with magic will openly use at least part of their true name, never realizing its significance. For example, a man named at birth "Nathaniel Dorthanson" may be known by all as "Nate the Smith," bur Nate the Smith will not work as a true name. For arcane importance, even the pronunciation of the true name is significant.
Any magical creature and most adventurers and intelligent monsters will most likely hide their true name as the treasure it is.
Animal intelligence creatures true names are very rarely known by any but the greater animal spirits and the gods. If for some reason the true name of an animal type is known and misused, the elder and namer gods will do whatever they can to punish the spellcaster responsible. Generally this means death for blatant abuses, though sometimes a god will simply wipe the name from a worthy characters mind.
Intelligent animals, creatures and elementals each have their own true name.
In general, area effect spells cannot be augmented by a true name, except in that they are harder to resist for targets whos names are invoked.