Feel free to comment or ask if you want any clarifications.

Spells

[[Golden Harp]]

Most (if not all) water decks deal only strike damage. So if you can manage to get this on an ordinary site nearby and keep it there, they will be unable to kill you at all. Just try to play it AFTER they use a spell that burrows artifacts if you're playing against earth.

[[Blasted Oak]]

MVP in any game you can draw it, but you'll only have a 33% chance of getting it on a good day. This artifact messes up any spell that targets an artifact, site, or minion. Just make sure to keep a minion on the site if you can for [[swap]], so the opponent is forced to target the blasted oak and your minion. No one I've played against has figured out that you can swap my makeshift barricade and my blasted oak yet, but you don't want to bet on your opponent being ignorant in a tournament setting.

[[Makeshift Barricade]]

The damage replacement for this card happens AFTER the damage reduction for [[Ironclad]], which means that anyone dealing you damage directly needs to do at least 5 damage to break the barricade. [[Lord of Lies]], [[Gnarled Wendigo]], and [[Dormant Monstrosity]] are usually the only cards that are run in water that can break through this, so this will keep you safe in most cases if you already dealt with those threats. Again, wait to play this until after Atlantean Fate is played if you can help it. Try to place an ordinary site as your home site to help with this.

[[Root Spider]]

This has way more opportunities to die than against other matchups, but there is one very important use-case. If you have an ordinary site as your home site, you will be untouchable if you play a root spider beneath you. As long as there are no voids next to you. [[Lacuna Entity]] is the real killer for root spider, in addition to fate.

Sites

[[Common Village]] / [[Humble Village]]

This should almost always be your home site. Because it's ordinary, it's not vulnerable to [[atlantean fate]]. And atlantean fate WILL be played in 100% of the games you play somehow.

[[Gnome Hollows]]

This is a great potential home site if your biggest concern in [[Ruler of Thul]] or [[Aino]]. Prevents him from coming into your back row in most cases. Unfortunately, it's susceptible to [[atlantean fate]]. It's best to not rely on this for protection on death's door, unless they've already used their atlantean fate or you've dispelled it.

Site Placement

You generally want to make a " T " formation to start. By turn 3/4/5, you should know if you have enough ramp to start encroaching on their side of the board or not. If you can confidently take at least 2 of their sites away, that will be enough to be worth it. If you keep their sites limited to 8, then they can't cast [[Lord of Lies]] + [[Swap]], or [[Ruler of Thul]] + [[Atlantean Fate]] on the same turn anymore. Then you can hopefully deal with the threats one at a time.

If you don't have the ramp to start encroaching in their space, you probably want to retreat into the " M " formation. Keeping only 1 entry point to your site is very helpful in controlling the flow of movement and can ward off a lot of threats. That being said, fill in the voids if your opponent is playing minions with voidwalk or hasn't played their [[Lacuna Entity]]s.

If you face water, you want the hollows as your home site, with an ordinary site somewhere nearby. This is to prevent a surprise [[Ruler of Thul]] attack. This does leave you vulnerable to [[Atlantean Fate]], but you can just move to a nearby ordinary site or something. For every other matchup, you can make your home site whatever you want. Gnome hollows is usually best played on the front lines, though.

Opening Hand

For your opening hand, it's generally a good idea to have some kind of ramp spell and some kind of turn 3+ play. You'll also want to keep any card draw you get. For ramp, you ideally want [[Landmass]], but [[Kettletop Leprechaun]] is a good consolation card. [[Common Sense]] is good as a third best option to search for a landmass or to keep for the later game when you need a [[Makeshift Barricade]] or [[Border Militia]]. You'll generally want to mulligan any card that costs more than 5 just so it's not sitting in your hand for 6 turns if you don't get the best ramp. For card draw, [[Morgana le Fay]] and [[Searing Truth]] are great keeps.

No matter what you mulligan, though, you shouldn't feel bad. As soon as you use a [[common sense]], you will shuffle your deck, so it won't be on the bottom anymore.

For sites, you want to try to hit an ordinary site and/or a [[Gnome Hollows]] in your opening hand. Any of the Villages will also go a long way for preventing yourself from getting fate'd. Mulligan or keep the rest depending on your threshold requirements.

Other good cards in your opening hand you can keep:

[[Blasted Oak]], [[Root spider]], [[Torrid Omphalos]], [[Toolbox]], [[Golden Harp]], [[Morgana le Fay]], [[Gargantula]], [[Archangel Michael]], [[Quarrelsome Kobolds]], [[Gigantism]], [[Earthquake]], [[Death Dealer]] (maybe), and [[Poison Nova]].

Cards you do NOT want to keep in your opening hand:

[[Arjaro Exorcist]] (situational, good against water, air, and [[Enchantress]]), [[Border Militia]], [[Onslaught]] (Unless you have minions you know will stick around), [[Boudicca]], [[King of the Realm]], and [[Balor of the Evil Eye]].

Tells

Usually players will set up their plays before they happen. If your opponent has 1 or more minions on their back row and are not moving up, expect a [[Ruler of Thul]] next turn.

[[Atlantean Fate]] is hard to predict, but if you see something like a [[Ruler of Thul]] come down and not attack, then they are most likely waiting until next turn to play their fate and disable your home site [[Gnome Hollows]]. Also, if they attack onto your sites with important minions that have submerge, that might be a tell.

If there is a minion with 4+ power on the board, it's pretty safe to just always assume that the player has [[Whirling Blades]] in hand. So make sure you play accordingly.

MATCHUPS

🌊WATER🌊

Secondary Threats - [[Whirling Blades]] | [[Grapple Shot]] | [[Call of the Sea]] | [[Acid Rain]] | [[Aino]]

🪨EARTH🪨

Secondary - [[Cave-In]] / [[Bury]] | [[Paladins of Bazia]] | [[Border Militia]] / [[Guards!]] | [[Garden of Eden]]

🌪️AIR🌪️

Main - [[Whirling Blades]] | [[Sphere of Animosity]] | [[Daperyll Vampire]] | [[Disenchant]]

Secondary - [[Sturmgeist]] | [[Grapple Shot]] | [[Feast for Crows]]

🔥FIRE🔥

Main - [[Courtesan Thais]] | [[Scorched Earth]] (with [[Roots of Yggdrasil]]) | [[Balor of the Evil Eye]]

Secondary - [[Morgana le Fay]] | [[Poison Nova]] | [[Shatter Strike]]

Trench Warfare

@Jack B