I'm trying to wrap my head around how Falke's talisman (described on page 96 in Guardians of the Forest) can change size to accommodate her heartbeast transformations.
Shouldn't the change size effect have added magnitudes since it is made of silver? The base effect at level 4 only affects dirt.
Also, how often can she use this effect? It is designed as a constant effect with two uses per day but I assume that the effect is triggered on every transformation? Wouldn't the uses per day have to be higher to accommodate for this?
It looks like not having '+2 Metal' is a missed error that should be errata. 'Change Size' should be level 20, with a Final level of 27.
The write up is hard to understand, but the changing size is a constant effect. The first 'Triggered' in its description is not about using one of it's daily uses, but when it receives a notification from the first enchantment (by the Linked Trigger) that it adjust the size to fit Falke's new form.
Constant effects are always active. If you don't want to have to do something to adjust them, then you add in sensory effects with triggers. The anklet could always adjust its size from the second enchantment but without the first Falke would have to do some 'triggering activity' (ie use an action) to make it adjust. The first enchantment detects when she shape changes and automatically sends the 'triggering activity' to the second without her doing anything.
I do not understand why "changing shape" cannot count as the triggering action. After all:
A trigger can involve a command word or phrase, moving the item in a specific way (for example, waving or pointing a wand), a stance to be adopted, or anything physical that you can imagine.
Actually, my troupe would go for a Base 4 (+2 metal) effect "Change a ring, necklace etc. in a major unnatural way - so that it's always a perfect fit of its wearer". A common magic item trope, we find it much more "mythical" than event-driven enchantment programming! The result would be MuTe Level 24 (Base 4, +2 Metal, +2 Sun, +4 Levels constant effect).
We mentioned something similar to each other in passing before on the gem to detect aura type. The writers always seem to overly complicate constant effects with sensory trigger effects (although this one is only a single sense, not four!). My group would most likely use something similar to your example.
I was attempting to explain why the writers did it the way they did. Also some groups require a triggering action to actually take an action, thus actually needing the sensory effect trigger. That really comes down to YSMV, some wanting simple and some wanting complex.
EDIT: The writers seemed to want sensory effects to be a requirement, even though they wrote a large loophole in the rules that would allow many things not to need them. However most of their published designs, at least early on, always used sensory effects rather than the loophole when possible.