Dr. Egon Spengler: 'Vinz, you said before you were waiting for a sign. What sign are you waiting for?' Louis: 'Gozer the Traveler. He will come in one of the pre-chosen forms. During the rectification of the Vuldrini, the traveler came as a large and moving Torg! Then, during the third reconciliation of the last of the McKetrick supplicants, they chose a new form for him: that of a giant Slor! Many Shuvs and Zuuls knew what it was to be roasted in the depths of the Slor that day, I can tell you!' - Conversation Unearthed from an ancient crypt, possibly related to Yog? Recording this in my journal for further review. R.F., 11/26/2249
This faction, headed by the Outer God Yog-Sothoth, consists of the cultists and monsters who serve it. They are masters of portals and keys. They seek knowledge, but too much leads to madness.
Yog-Sothoth Themes You Can Use
I've listed several of Yog's strengths below. Choose one of to match with a buddy faction, or combine several for mono-Yog goodness, opening up cards like Across Dimensions and Disciple of the Gate.
Bring Out the Gugs!
Gugs are a special subtype of Yog characters. Generally, they share the following characteristics: They bring a nice quantity of skulls to the table, but they actually want to get wounded, triggering special effects. They come with Toughness +1 to enable them to be wounded and still operate. Many of them have book icons as well, but you'll generally be light on terror and clue icons.
Enraged Gug is a good example of your typical Gug. Cost 4, he brings 3 skulls, 5 skill, and toughness +1 to the table. He also has a Response allowing you to wound an opponent's character when he is wounded. The nice thing is that you don't need to choose a character committed to the same story (or any story at all), the only restriction is the character have one skull icon. Laboring Gug allows you to draw a card when he's wounded, and Gug_Sentinel allows you to exhaust one of your opponent's characters. Wandering Gug gives you a taste of discard. No gug focused deck would be complete without Puj-Dunk, who only needs to be wounded to bring another Gug into play. Once you stack enough Gugs, Living Mummy's forced response becomes deliciously overpowered.
You can buff your Gugs with a City of Gugs to allow them to take more wounds (and dish out more special effects). Alternatively, you can multifaction Syndicate and use Dutch Courage instead, which doesn't share the Day restriction, allowing you to play Great Stone Circle and force the combat struggle ahead of the terror struggle, as long as it's night. Ascension to Zura lets your remove a wound from an exhausted gug and ready him, potentially surprising your oponent and breaking his carefully calculated attack. Sadly, Slavering Gug from Shub doesn't have the Gug subtype, so he can't take join in the fun of these support cards, although you might include him just for flavor.
Focus on Spells and Events
You can use Yog very successfully as a buddy faction for events, his are some of the most powerful in the game. Yog gives you unrivaled access to your deck and discard pile. Speak to the Deadlets you place 4 cards into your discard pile from your deck, and then choose any two cards from your discard into your hand. This is a great way to simply draw cards, being able to choose which of the 4 you like the best, but is also nice because you can grab needed cards out of the discard even if they weren't generated as part of the draw. Gathering at the Stones is a cheaper version, costing only 2, but you only get one card out of the discard, and it needs to be there already. All are One lets you see the top 3 cards of your deck, and enables you to get rid of the worst of them, as well as placing the best immediately into your hand. Journey to the Other Side lets you plan ahead based on what you have coming, and move the most advantageous cards up to the top, even getting to keep one if you can overpay.
Not every Yog Spell involves card sorting. A single glimpse forces your opponent to sacrifice a character, and can be brutal early game if the oponent has brought out one big beast instead of a bunch of disposable birds. Sacrifice is particularly nice because it bypasses things like invulnerability, and doesn't cause things like Eat the Dead to trigger. Casting off the Skin is a nasty little surprise that scales nicely as you and your opponent accumulate characters and clash in massive battles. Unspeakable Resurrection lets you bring a character from your discard pile directly into play. It scales nicely as a cost X, and if you time it right you can disrupt an opponent's attack by bringing one more defender than they expected to your choice of stories. Chant of Thoth lets you bring spell and artifact cards back from your discard to batter your opponent once again (or play a Yog-Sothoth Lord of Time and Space to do so as often as you want to pay for it. Combine it with a Opener of the Gate and you can bring your monsters back from the dead as well. With an opener out the classic version of Yog-Sothoth (In Whom the Spheres Meet) can become very affordable.
If you can force your opponent to run out of cards in his deck, you're granted an automatic victory, and no faction has the ability to do so like Yog. Combine a Blackmoor Estate along with multiple Terrors in the Dark to create the backbone of your discarding force. Curse of the Stone provides a one time dicard that scales over time, and Gatekeeper can allow you to force a discard as long as you're dominating icon struggles. Hermetic Scholar and Things in the Ground both force you and your oponent to discard, but you shouldn't mind if you're forcing him to discard through other methods.
Generally when you're attempting to win by making your opponent discard, you don't want to actively pursue victory through struggles. Instead, play as defensively as possible. Slow your opponent from winning investigation struggles, perhaps with a The Setting Sun. Find a way to defend, either through a card like Hideous Guardian to absord wounds, or a card with invulnerability to defend alone (Guardian Pillar works here). Don't worry about your opponent winning some victories, as long as you can hold out until your discard turns the tide
Yog characters stand well on their own, although you won't find an overwhelming force of terror and combat like Cthulhu or Shub. Doppelganger lets you make an exact copy of any character in play, giving you an answer no matter what your oponent throws at you, and playable early or late in the game. Cannibal Ghast makes a great early defender, with a ton of skill for only cost 1, and Tcho-Tcho Tribe can take over at the end game, gaining a huge bonus for defending alone. The Sleepwalker is a good early striker, able to prevent a character with a skull icon from opposing her, and having a terror icon she's all but guaranteed an early success. Guardian of the Key is a nicely balanced early card as long as you have the appropriate resources to cover the "Loyal" cost modifier, and Wizard of Yog-Sothoth becomes a beast when it's night. Guardian Elder Thing can make your opponent very reluctant to commit anywhere as long as you have the resources to trigger his effect.