Relevant "prey" + "only" rule for reference :

If an enemy's prey instructions contain the word "only," that enemy only moves towards and engages that investigator (as if it were the only investigator in play), and ignores all other investigators while moving and engaging. Other investigators may use the engage action or card abilities to engage the enemy.

• Non-bearer cannot stand on its way to get the engagement. It is also costly to help because you need an engage action.
• If the bearer got eliminated/resigned from the campaign it simply stay still and everyone else can pass through.

This card is bad with Lola (its like they don't want her to be viable), but is extremely good with Charlie, especially late game. Charlie can very conceivably have a card from all classes up given his extremely diverse card pool (e.g., typical pick is guardian and survivor for his card class. In an enemy handling deck, you could then grab David Renaut, Delilah and a Med Student. You now have all five classes in play).

That translates into a +5 attack that does six damage, a serious boss killer card.

As others have said you're going to want to sit on this card a bit, especially Charlie, to get the full effect. But once you've got a rainbow assortment of allies on the table, fire at will and watch the cackling politican send his army of free lancers into the boss' maw.

In addition to @olahren review: William has a nice interaction with Mariner's Compass, Fingerprint Kit, Archaic Glyphs and other multi-clue cards. If you find yourself investigating a location with one clue, you can now grab that second one from somewhere else.

Charlie is a disabled old man with a cane and a bad smoking habit, until you play him off taboo.

Off taboo, he's a machete wielding lunatic who swarms his victims with a pro football player, dogs, a literal assassin and his trusty secretary. He uses Dig Deep and Drawing Thin to ace will/evasion checks, physical conditioning or combat training to buff his machete and loves explosives. He's even ever vigilant for eldritch horrors, and has no problem going Toe to Toe.

Don't count this guy out, unless you play taboo. I'm not sure how to play him without the ridiculous resource generation from Drawing Thin.

Tldr

Off taboo, starter deck should be In The Thick of it, Drawing Thin x2, Ever Vigilant x2, Jessica Hyde, Peter Sylvester, Physical Conditioning x2, Machete x2, Guard Dogs x2, Dynamitex2, Hallowed Mirror, Dig Deep then whatever you want.

This mitigates his biggest problem which is playing assets, and let's you do one (1) really good combat check per round. He's otherwise extremely tanky, but due to the fact he only gets one "good hit" hes dependent upon card effects that guarantee damage.

That's not enough to be a solo mob healer imo, and he will usually need to be paired with someone who can handle enemies just fine on their own (i.e. trish) but his strength comes from being able to do anything really, really well, one time per round.

"Two pennies saved is a penny earned"

I got to try Embezzled Treasure recently in a big-money Jenny Barnes deck, and this was an all-star. I don't think every rogue will want it, but for those who do it is for all intents and purposes a 0xp Another Day, Another Dollar that costs an action but will frequently net you more resources that you can share with your friends.

Specifically, those who want it are any rogue with more money than they can use in the lategame. Big money builds are the obvious choices here, but rogues that use money making engines like Lone Wolf, or have their resource expenditures frontloaded into assets and setup turns can also use it.

In particular, decks using Underworld Market or any other illicit synergies will find this useful. The market keeps Embezzled Treasure from clogging your hand and draws, while reliably giving you access to it early enough to start loading it up with resources. And if you're running Fence or "I'll take that!", you can get this in play without even spending the one action!

While I think this card is very strong, there are a few caveats I would be remiss not to mention. First, this is a campaign-only card, utterly useless for one shots. Second, there is an awkward timing issue with this card. The action cost to play it (sans Fence) is not negligible, and you need to play it at least 5 turns before the scenario ends to get full value. Finally, while I think a committed Big Money deck could support both copies of this card, this feels to me like a perfect one-of.

All that being said, the next time you're rolling in money, save some away for a rainy day. You and your friends will be happy you did.