The lack of a true name restricts the summoners power over Nameless, summoning is not just the use of the name but is often accompanied by focus items, see the summoning of the Erl King in Dead Beat all designed to re-in force control over the summoning. You require every advantage in dealing with a more powerful being, and the closer to the true name the better. You might therefore summon Nameless with the name Talvi Inverno, but not be able to control the summoning resulting in Nameless being able to attack you with impunity. Similarly a death curse aimed at Talvi Inverno may not land with full power if Nameless is not in front of you to focus on his physical self.
Talvi Inverno is actually Winter Winter, it’s not really a name (but sounds like one) but is actually a descriptor of his allegiance to Winter. You might therefore accidentally summon one of the Winter Queens using that name unless you used additional focus items specific to Nameless. See the point ? the lack of a true name adds a new degree of uncertainty and danger to any ritual such as tracking, summoning, binding, cursing etc.
If I was going to do any of the above a business card (I doubt he gives those out given he is VERY exclusive) or headed signed notepaper would be a good focus item, failing that a stack of recorded cases Talvi Inverno won would be the best option, but these would contain other true names. It should be noted that in Even Hand that Marcone mentions letters from his lawyer, at this point in the timeline that would be Nameless (so yes we had mention of Nameless before The Law, just not by name, of course) so Marcone has personally signed correspondence from Nameless, giving him a hold over Nameless. Nameless probably has Miss Lapland pp inter parties correspondence and send e-mails on his behalf otherwise - he can’t get away with that for court filings requiring his original signature, so unless you are Marcone you would need to break into the court office to get his original signature on an filing to aid as a focus. I bet there are few viable photos of Nameless as well to act as a focus - neither Bob nor Gary mention one, and slippery customer like Nameless would likely have some magical protection against his image being recorded accurately, to preserve his anonymity but also deny a use of an additional focus. Of course he would litigate as well to preserve his anonymity.
It is basically a loophole in a lot of magical practices aimed at an individual, and Nameless is of course a lawyer, well placed to exploit it. Just one of the reasons I think Nameless is Cowl. Both go by alias and are careful about preserving their anonymity. Try to track Cowl and you have nothing to go on, and under that you have the uncertainty of Nameless, unless you know Inverno and Cowl are one and the same and have additional focus items for Inverno. This suggests Harry would have to ask for Marcone’s help in tracking Cowl when a link between Cowl and Nameless is established. Now that fits into the narrative.
