Rules semi-commonly misplayed

Setup

• The Invaders Explore as the final act of Setup. (Unless you are deliberately making the game easier.)
• Your Unique Power Cards start in your hand. (These are the Power Cards with your Spirit's portrait on the back; there are usually four.)
• You don't start the game with any Energy unless your setup instructions say so. Your Energy for Turn 1 comes from Growth and your top Presence Track.
• In a late-breaking errata, unless you are using the board from Horizons of Spirit Island, add 1 extra Blight to the Blight pool, regardless of player count. This helps with balance compared to the printed rule.

Spirit Phase + Powers

• A number over an arrow means Range - not "how many Presence to add"!
• You only get the highest value from your Energy Track and Card Plays Track – you don't add them together.
• The "Reclaim One Power Card" Presence-track effect can be used every Spirit Phase, starting the one it was uncovered.
• You can't resolve any Powers until the 'Fast Powers' phase – by which point all Power Cards must have been paid for already. So if someone's short the Energy they need this turn, Boon of Vigor doesn't give it to them in time.
• You don't choose targets for Powers until they are resolved – especially, you don't need to decide where to use a slow power until the 'Slow Powers' phase.
• Each new line of a Power is in addition to everything else the Power is already doing. If two effects of a Power are mutually exclusive, the Power will either grant you an explicit choice between them or say that a later effect happens "instead" of an earlier effect (usually as a bonus for having more Elements).
• Each Power can only do things in the single land that is its target, barring explicit instruction or Gathering from / Pushing to adjacent lands.
• Many Power Cards have restrictions on the target land, which are easier to miss than I'd like with the current graphic design.
• You get Elements as soon as you play a Power Card during the Spirit Phase, not when you activate the card later in the turn.
• Elements are never used up - Innate Powers, Major Power thresholds, and everything else that cares about elements just checks how many you have, it doesn't "spend" them.
• Elements are not shared - Each Spirit only gains the Elements from the Power cards they played this turn.
• Reclaim cards means reclaim all cards. – The Growth option to reclaim cards allows you to take back every single card that you've discarded, not just one. This is different from the "Reclaim 1" ability found on some presence tracks and on Bringer of Dreams and Nightmare's second growth option.

Invader Actions and Blight

• Dahan provide no intrinsic defense to the land (or themselves) – during Ravage, Invaders deal full damage to both the land and Dahan simultaneously.
• Dahan only attack on their own when the Invaders Ravage the land they're in (and do so after taking casualties) – they don't attack every turn, or when Pushed.
• Damaged Invaders and Dahan still deal full damage – the amount of damage dealt is not affected by the amount of damage taken.
• When Invaders Ravage a land, it adds at most one Blight there, no matter how much Damage the Invaders do (though you might cascade elsewhere, if the land already had Blight). You don't add one Blight per 2 Damage; that can lead to a quick, nasty loss.
• Invaders deal damage to both the land and the Dahan simultaneously – damage to one does not decrease damage to the other, so 2 Damage (say, from a Town) will destroy a Dahan and add a Blight.
• After adding Blight to a land with Blight, you also cascade (add 1 additional Blight) to exactly one adjacent land. – Pandemic's mindshare in the co-op zeitgeist makes misremembering this as "all adjacent lands" understandable, but doing so can lead to an astoundingly sudden loss. Also note that the cascaded Blight is additional – you still place the original Blight! (Again, unlike Pandemic.)
• Build and Explore add new Invader pieces – they don't replace existing pieces.
• Builds take place whenever there are any Invaders present – any white pieces, not just Explorers (the figures of people).
• Oceans are a source of Explorers in addition to Towns and Cities. But Explorers are not themselves a source of Explorers.
• Invaders destroy the Dahan efficiently – when assigning damage to the Dahan, you can't spread it out to avoid destroying them. (When assigning damage to the Invaders, you can spread it out as you wish.)

General

• Destroying Towns and Cities causes Fear - some Power cards provide Fear directly, but the largest source of Fear is usually 1 Fear per destroyed Town and 2 Fear per destroyed City.