Here is my attempt at a competitive mid-range deck made from the best stuff in Earth! I like this deck enough that I took the time to update the primer to be much more thorough and cover every one of my card choices. Let's burrow in:

Artifacts:

Onyx Core remains an inclusion that is welcome more often than not. The benefits of drawing it early are obvious, but even late game it essentially provides an extra ward for some positive tempo plays.

Toolbox/SilverBullet replaces Common Sense and frees up a lot of slots in the main deck so you don't have situational ordinaries/exceptionals like Dispel and Divine Healing taking up space there.

Holy Water (collection) is another ward for anything that needs it, particularly something that has lost its initial ward and is crucial for maintaining your board presence. Also useful for getting rid of large evil threats that are unaffected by Bury/Cave-In.

Pnakotic Manuscript plays well enough with warded minions immune to the damage or supported by Lady Iseult, Crown Prince if you have another mortal, or Kettletop to trigger its ability.

Auras and Magic:

Crusade is an automatic inclusion for any mono-Earth deck. Ideally you want it early and placed on your opponent's side of the board for maximum aggression.

Tithe can potentially extend the time you have to keep drawing spells instead of sites for each of your turns. Casting it early also gives you greater selection of which sites you get to place in a deck that doesn't play Crossroads.

Dispel (collection) is most often a Toolbox target for when you need to get rid of a particularly troublesome aura or artifact, or to stop an Enchantress or Battlemage from running you over.

Border Militia is a versatile little ordinary that can provide you with some cheap fodder for slowing down enemy aggression, or overwhelm the board later when combined with King of the Realm. Just be careful if you choose to use it against Battlemage because they can easily turn it into a lot of card advantage if they manage to find a timely Screaming Skull. Be careful about using this when Order of the White Wing is on the board!

Bury (collection) is a cheap, staple removal spell that only tends to be bad against Water decks. Don't forget that it can be used to burrow artifacts and potentially deprive your opponent of their benefits if they don't have a burrowing minion to retrieve them.

Call to War has a lot of worthy targets in this deck and acts kind of like Rescue if your aim is to replace a dead exceptional mortal and you need your Toolbox for something else. Take Shield Maidens first as they are generally your best exceptional mortals.

Rescue (collection) has a lot of situational usefulness. Lady Iseult and King of the Realm are excellent minions that are sadly easy to kill, so being able to fetch Rescue on demand can help maintain a favorable board state with them.

Cave-in is similar in utility to Bury, but has more potential to punish over-committed opponents at the cost of one more mana and not being a Toolbox target.

Gigantism is an infrequent but always welcome spell with its ability to turn even a lowly foot soldier into a serious threat for a single turn. Use it wisely!

Earthquake is a game-changer more often than not for its ability to kill multiple minions at a reasonable cost and switch sites around to make them more vulnerable to attack in the absence of Crusade. It's naturally less effective against decks with a lot of water sites, but you can still move things around to open them up to more advantageous angles of attack, potentially breaking up bodies of water to strand dangerous enemies like Mester Stoor Worm and Giant Shark.

Guards! gives you some serviceable cannon fodder in a pinch and can help close out games in tandem with King of the Realm, Bannerman and/or Shield Maidens. Be careful it doesn't overlap with Order of the White Wing!

Landmass helps you ramp into the mid game as a mini Tithe to ensure you can afford to ward important minions on curve.

Pendragon Legacy can get back all your VIPs and even unique sites that may have been destroyed, giving this deck an edge in especially grindy games.

Minions:

Carrion Beetles (collection) is here to counter Archimago for the most part.

Revered Revenant is a cheap and effective minion that only works in a Savior deck. You will usually play this with a ward on turn 2, but can sometimes get away with it on turn 1 if your starting site is a Blessed Village or Pilgrim's Shrine.

Angel Ascendant is another cheap minion that really wants a ward, worth holding for a turn if your opponent is off to a slow start..

Holy Warrior comes pre-warded, so he serves as a good companion to a Revenant and is a solid defender against early aggression.

Kettletop Leprechaun having deathrite means you want to be aggressive with it to draw a site, and only give it a ward if you really need it to defend for a turn.

Lady Iseult is the classiest dame on your side of the board and does a fine job of maintaining your board presence in most situations. She can allow you to be a bit more aggressive even with your smaller minions given that they come right back to your hand if they die. She is unfortunately rather easy to kill due to being low-power and needing to be nearby the front lines, so try holding a Toolbox for a Rescue in order to keep her around longer. She can also benefit from the protection of sites like Gnome Hollows and Dome of Osiros depending on the situation, so placing those sites forward is ideal in an Iseult game.

Crown Prince is another early minion that holds the line and synergizes well with some of the other cards. He performs well early on under a Crusade and even later with King of the Realm sitting somewhere relatively safe.

Root Spider is another high-utility minion with a lot of value for its low cost. It can single-handedly shut off avenues of attack from non-burrowing minions and save you from an early onslaught when used correctly with other defensive cards. It can also be used aggressively, pushing forward and disabling defenders while you gain more ground towards overwhelming your opponent's side of the board.

Order of the White Wing is an all around solid minion that punishes reanimator decks and cards like Necromancer and sites that produce tokens.

House Arn Bannerman acts like a mini King of the Realm that can also buff your non-mortal minions. Definitely worth a ward, and a great target for Call to War if you already have Shield Maidens on the board.

Royal Bodyguard makes you and your royal VIPs even harder to kill. Very good ward target.

Archangel Michael is a lot of value for a mere 5 mana. Getting a free step and strike makes him invaluable in ward mirrors.

Shield Maidens are utterly busted in a Savior deck and your main target for Call to War because of this. Ideally you want multiples nearby each other because their abilities stack and you hate the idea of your opponent having anything resembling fun.

Scent Hounds (collection) is a cheap solution to annoying cards like Morgana and Infiltrate. Can and probably should also be warded against decks using such cards, as they tend to pack a lot of removal.

Vivien the Enchantress can be game-changing against avatars with high-value abilities like Necromancer and Animist. She can always be used to play or draw an additional site per turn and is almost always worth warding.

King of the Realm makes all mortals yours to command and strong enough to close out games with the help of Border Militia, Shield Maidens and/or Crusade. He only gets thwarted by King Arthur or another King of the Realm played after, so keep removal handy if you anticipate your opponent playing these cards. He is generally more valuable staying safely in the back row or ideally nearby wherever Lady Iseult happens to be.

Tragedy Worrywart (collection) can be a lifesaver against any deck packing a lot of damaging spells thereby negating your ward strategy.

Sites:

City of Souls provides an excellent source of free mana for your avatar to keep pumping wards. Best placed in your back row to reduce the chance of your opponent exploiting its drawback.

Dome of Osiros is a great defensive site for one of your MVPs to hang out in, like Vivien or King of the Realm. Also acts as a massive speed bump if your opponent can't muster removal for whatever you have parked here.

Haystack is somewhat of a flex slot, but well worth it when it gets to punish combo decks running fetch cards. Also neutralizes Murder of Crows quite effectively.

Kingdom of Agartha is another flex slot that tends to be more useful against decks running a lot of minion removal. It also allows you to be more selective with how you use Savior's ward ability because burrowing minions are generally difficult targets for spells.

Gnome Hollows is a life-saver against any minion big enough to be a true threat to your avatar, making it an ideal first turn play to serve as an effective hideout in most games.

Mirror Realm does just about whatever you need it to. It can copy useful enemy sites if need be, or can serve as an extra copy of your more important sites like City of Souls for even more ramp.

Mount Ussar Sanctuary is rather self-explanatory. It's probably best placed in the back row alongside another defensive site like Gnome Hollows.

Pebbled Paths stops charge minions so they don't get free attacks to break your wards.

Pilgrim's Shrine is another power source for your Revenants and a free ward for anything.

Pillar of Zeiros might actually be the only site you'd rather not draw early, as its utility is generally greater the longer the game goes on. It can save your life against burn strategies with massive life gain and makes for a great potential hoser against dedicated cemetery strategies. Remember that this affects both cemeteries, so you might want to Rescue something before playing it.

Rift Valley is best used early and aggressively as a means of opening up another avenue of attack against the opponent's side of the board. It's not quite as powerful as Crusade, but it can serve well enough if played correctly.

Snapple

@JMK