I like this card, 1 resource for 1 extra health and sanity, that's a fantastic conversion of resources.

Sadly, liking cards isn't the same as them being good. First off, Dodge exists, a card that costs the same amount of resources and is very likely to net you the same amount of damage sustained or more. Take for example the core set campaign, Dodge immediately has superior payoff if you save it for the confrontation with Ghoul Priest, not every scenario has such a good example but most will present you with some route to preventing 2+ points of horror/damage.

Perhaps the most important benefit in Trusted's favor is that it also protects against treacheries, but that strength is moot against the fact that it has the added clause of needing an ally target, not to mention that allies might not stick around long enough for you play Trusted on them in the first place while Dodge is fast.

Should you play Trusted? Yes, try it. Keep in mind however that it should only be played in an ally heavy deck with more ally-support cards like Charisma, Inspiring Presence and especially Calling in Favors, it happens that Trusted helps your allies stick around and those other cards all depend on allies sticking around until you get an opportunity to heal them, swap them around or fill your board with them.

In summary: Play Trusted as a mechanic to fortify your allies to then combo them with Ally based mechanics. An extra shot with Beat Cop, an extra trigger on Aquinnah. An extra bite from your Guard Dog. Extra tank on your Art Student before you Calling in Favors on them and replay them.

Scavenging can be used to recover Backpack, so you can drain your deck of items pretty quickly.

If you discard the Backpack with assets below it (by playing another body slot item), you can fill your discard pile with more targets for Scavenging.

This is especially useful for investigators with high and access to seeker cards, like Minh Thi Phan or Rex Murphy.

With so much time having gone by since the release of this card, I thought it might be time for a re-appraisal. While I still think it's fairly weak, as far as signature cards go, the card pool has expanded vastly since the Core Set, giving this card a total of 20 spells to work with (including her weakness). Let's take a look at how likely it is to play six spells over the course of a game nowadays.

Very beneficial to Agnes is the fact that many newer spell events are fast. For instance, Aggy gets a free draw from Hypnotic Gaze, Ward of Protection, Mind Wipe, Counterspell and Time Warp. All of these are perfectly reasonable includes for Agnes, so her odds of getting a double benefit from them are good. In the same vein, many spell events take actions that you might be taking anyway, giving you another double benefit situation with her necklace out. These include Astral Travel, Bind Monster, Blinding Light and Storm of Spirits. Uncage the Soul isn't a spell, but it does put spells into play very cheaply for Agnes, so in a way it triggers the amulet. Getting a free draw for playing spells even makes some sub-par includes like Alchemical Transmutation and Recharge more attractive, since she gets the draw even if the spell fails. Running a doom-heavy deck? Moonlight Ritual is a spell! Free draws!

With the variety of spells necessary for this to be decent in place, we come to the other problem with the card: that darn accessory slot. While Holy Rosary is obviously terrific for Agnes, she has other options to bring her up to six at level 0; specifically David Renfield. I'm not saying she shouldn't run the Rosary; it's incredible on her. But I do think the Heirloom has enough triggers in the game now that it is competitive for the slot, and makes Relic Hunter a very tempting include for her.

Are all the problems solved? Is it worth playing late? Is it as good as Zoey's Cross? Absolutely not, but I think it's a much harder decision now whether to mulligan it out of the starting hand or play it first turn over Rosary. In a deck that's built around having spells to play, which is totally realistic now, it would be a very powerful card.

Spells continue to be released, and they can only make this more powerful.

This card really screws you over more often than not. Green Man Medallion is great, but Sacrificial Beast often spawned in a locked location, essentially blanking Jenny and Lone Wolf for entire scenarios for me.

Defiance, eat your heart out. (Worth it!)

This card is basically insurance against the chaos bag. All of those narrow "I am fine so long as I don't draw this token" situations can now be eliminated due to this card. It works really well with cards that draw multiple tokens and might have some interactions with ritual candles (which, again have interesting interactions with multiple token draw cards).

Add in some token sealing and you have some consistent tests. Most mystics will like this card, but it will really shine in any investigator (Jim Culver and Father Mateo especially) that is considering the upcoming Olive Mcbride and Dark Prophecy.

-Edit-

This card does some serious work with Premonition, Olive McBride and Dark Prophecy. I also think that this package is particularly potent in Sefina Rousseau as she also has a pretty bomb diggity elder sign trigger AND she can play premonition on tests with cards like Double or Nothing.

So in closing, this card is amazing. Play it with Premonition, Defiance, Dark Prophecy and Olive and you should be well on your way to having a consistent experience through Hard difficulty.