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.

I am a bit surprised there isn't more buzz around this card, more action compression for Survivors is huge. Between this and Sharp Vision (not to mention Resourceful to get them back) survivor is almost as speedy as some Seekers. Darrell's ability to take this, Sharp Vision, Deduction or Deduction(2) and Research Notes gives him silly levels of consistent action compression.

The auto succeed is useful for avoiding nasty token effects and the two extra clues is huge. The difficulty 0 requirement means this is only going to be consistent for investigators using Flashlight or Old Keyring, but that is a lot of survivors and fair number of investigators who splash survivor. With the new Old Keyring(3) this nets 3 clues from a 2 shroud location and 1 clue from somewhere else with auto success! If you aren't using those, you might be Darrell and getting to 0 should not be an issue.

Winging It, Lantern, Cryptographic Cipher, Otherworldly Compass, and Arcane Insight can also lower the shroud, but are secondary options since they only reduce shroud by 1 or you are less likely to have access to them.

This is most useful in 2-3 investigator campaigns where locations are more likely to have 2+ clues on them. Even though you may not profit as often from the extra clue from your location, remotely grabbing a clue off a location with a monster/locked door/high shroud is useful often enough for me to add this to solo Survivors as well.

OP card. As an first impression, Shed a Light seems to be similar as Exploit Weakness, and both have powerful effect but seems to be hard to play. However, in the game, reducing shroud value of the location is one of the main mechanism beginning with Flashlight, but reducing fight/evade value is not. In general, making 0 difficulty investigation is much easier than that of fight/evade.

Moreover, unlike Exploit Weakness, Shed a Light has good combo parts. We can play 2 Shed a Light (with Double, Double) at ONE investigation to discover total 5 clues (3 from here, 2 from any). We cannot play 2 Exploit Weakness at ONE fight/evade even aganist elite enemy because the second copy has no normal effect to replace which is already replaced by first one. In addition, auto-succcess guarantee you can trigger "succeed by (your )" abilites, such as Scavenging. With proper tool, you can trigger Scavenging robustly, regardless of your stat.

Here are some useful cards to reduce difficulty for investigation:

• : Winging It, Old Keyring(and 3lv), Gumption, Quick Learner
• : Map the Area, Unearth the Ancients(2lv only)
• Flashlight(and 3lv)