There's a lot of back and forth here so just want to clear this up, if the Q&A above is accurate, it's clear that:

1. Attacks of opportunity do NOT occur when the targeted location for investigation has an enemy. This is because attacks of opportunity occur when you spend the action, which happens at your current location before the investigate.

2. I believe in reading that, it can be assumed that attacks of opportunity do NOT occur when the target location has a massive enemy either. For the same logic above, attacks of opportunity happen before the application of an actions effect. Meaning there's no additional check for AoO on the targeted location.

I've still seen some doubt about massive enemies, but based on the Q&A here I don't see why there would be any doubt.

I am writing this fresh off of deck-building, running across a combo that makes this item far more viable than it might initially seem: Forced Learning.

This card, along with some other Survivor cards, suffers from only being useful when it is in your discard pile, which it is hard to get it into efficiently when not playing Wendy or Ashcan Pete. Having this in your hand means you have a dead card, and more often than not it'll be stuck there for a while.

Forced Learning solves this issue. Now, every upkeep, you get to put a card into your discard pile from your hand, without losing card advantage in the process! And the obvious beneficiary of this combo is Darrell Simmons, who may appreciate extra health soak in some campaigns due to his 6 base health (hello TFA), and also loves to have Winging it in his discard for more efficient clue-gathering. Plus, he can run Scavenging shenanigans as well due to his high base Intellect and tendency to lower difficulty naturally, which also synergizes with Forced Learning.

I'm excited for this, and I may have to update my review if it does not work out the way I'm expecting it to right now.

Looking at it again, maybe I should've put this review on Darrell Simmons, it seems quite specific. Although, Minh Thi Phan can also use all the cards mentioned.

If you take the action, do you have to take a tome? For example, if I am playing Daisy and the Necronomicon is my only spell in the top 6, do I have to draw it? The wording is a bit confusing.

Limited applications, but say Darrell Simmons fails a skills test on a Seeker Asset by 2. Granny Orne intercedes and he’s down only one. He immediately triggers the reaction on his Lab Coat to pass by zero. Could be worth the setup if you’re already recurring Fingerprint Kit, on a higher difficulty, for example.

A sequel to all the fight/evade reduction cards for Exploit Weakness, lets do the same for Shed a Light:

Guardian

• Breach the Door (The Scarlet Keys)

Seeker

• Arcane Insight (Path to Carcosa)
• Cryptographic Cipher (The Innsmouth Conspiracy)
• Map the Area (The Scarlet Keys)
• Otherworldly Compass (The Forgotten Age)
• Vantage Point (The Forgotten Age)

Rogue

• Momentum (Dream-Eaters)

Survivor

• Gumption (The Scarlet Keys)
• Lantern (Path to Carcosa)
• Lantern (2) (Return to Path to Carcosa)
• Old Keyring (Stella Clarke)
• Old Keyring (3) (The Scarlet Keys)
• Quick Learner (Stella Clark)
• Winging It (The Forgotten Age)

Neutral

• Flashlight (Core Set)
• Flashlight [lvl 3] (The Scarlet Keys)

A few notes:

• The Skeleton Key is very temperamental with Shed a Light. It sets the shroud to 1 after modifiers, so things like The Skeleton Key into Flashlight won't work. What will work is The Skeleton Key into a difficulty reduction effect, not a shroud reduction effect. So The Skeleton Key into Map the Area, Momentum, or Gumption (or Flashlight (3) amazingly, since the upgrade now reduces difficulty instead of shroud) does work to get a location's shroud to 0. (Edit: Thanks for corroborating this Dscarpac.)
• All these cards pair very will with a second keystone card: Lola Santiago. Take both her and Shed a Light for extra likelihood to get combo value from shroud reduction.