First off is the Devour keyword from the shard of Jund.
502.82a Devour is a static ability. "Devour N" means "As this object comes into play, you may sacrifice any number of creatures. This permanent comes into play with N +1/+1 counters on it for each creature sacrificed this way."
502.82b Some objects have abilities that refer to the number of creatures the permanent devoured. "It devoured" means "sacrificed as a result of its devour ability as it came into play."
* Devour appears only on creature cards.
* A creature with devour can devour other creatures no matter how it comes into play.
* You may choose to not sacrifice any creatures.
* If you play a creature with devour as a spell, you choose how many and which creatures to devour as part of the resolution of that spell. (It can't be countered at this point.) The same is true of a spell or ability that lets you put a creature with devour into play.
* You may sacrifice only creatures that are already in play. If a creature with devour and another creature are coming into play under your control at the same time, the creature with devour can't devour that other creature. The creature with devour also can't devour itself.
* If multiple creatures with devour are coming into play under your control at the same time, you may use each one's devour ability. A creature you already control can be devoured by only one of them, however. (In other words, you can't sacrifice the same creature to satisfy multiple devour abilities.) All creatures devoured this way are sacrificed at the same time.
Next, Bant's Exalted ability.
502.83a Exalted is a triggered ability. "Exalted" means "Whenever a creature you control attacks alone, that creature gets +1/+1 until end of turn."
502.83b A creature "attacks alone" if it's the only creature declared as an attacker in a given combat phase. See rule 306.5.
* If you declare exactly one creature as an attacker, each exalted ability on each permanent you control (including, perhaps, the attacking creature itself) will trigger. The bonuses are given to the attacking creature, not to the permanent with exalted. Ultimately, the attacking creature will wind up with +1/+1 for each of your exalted abilities.
* Some cards with exalted abilities have other abilities that also trigger when a creature you control attacks alone. Each time a creature you control attacks alone, both the exalted ability and the other ability will trigger.
* If you attack with multiple creatures, but then all but one are removed from combat, your exalted abilities won't trigger.
* Some effects put creatures into play attacking. Since those creatures were never declared as attackers, they're ignored by exalted abilities. They won't cause exalted abilities to trigger. If any exalted abilities have already triggered (because exactly one creature was declared as an attacker), those abilities will resolve as normal even though there may now be multiple attackers.
* Exalted abilities will resolve before blockers are declared.
* Exalted bonuses last until end of turn. If an effect creates an additional combat phase during your turn, a creature that attacked alone during the first combat phase will still have its exalted bonuses in that new phase. If a creature attacks alone during the second combat phase, all your exalted abilities will trigger again.
* In a Two-Headed Giant game, a creature "attacks alone" if it's the only creature declared as an attacker by your entire team. If you control that attacking creature, your exalted abilities will trigger but your teammate's exalted abilities won't.
Grixis' keyword, Unearth.
502.84a Unearth is an activated ability that functions while the card is in a graveyard. "Unearth [cost]" means "[Cost]: Return this card from your graveyard to play. It gains haste. Remove it from the game at end of turn. If it would leave play, remove it from the game instead of putting it anywhere else. Play this ability only any time you could play a sorcery."
* Unearth appears only on creature cards.
* You may play the unearth ability of a card in your graveyard no matter how it wound up in your graveyard.
* If you play a card's unearth ability but that card is removed from your graveyard before the ability resolves, that unearth ability will resolve and do nothing.
* Playing a creature card's unearth ability isn't the same as playing the creature card. The unearth ability is put on the stack, but the creature card is not. Spells and abilities that interact with activated abilities (such as Stifle) will interact with unearth, but spells and abilities that interact with spells (such as Remove Soul) will not.
* At end of turn, a creature returned to play with unearth is removed from the game. This is a delayed triggered ability, and it can be countered by effects such as Stifle or Voidslime that counter triggered abilities. If the ability is countered, the creature will stay in play and the delayed trigger won't trigger again. However, the replacement effect will still remove the creature from the game when it eventually leaves play.
* Unearth grants haste to the creature that's returned to play. However, neither of the "remove from the game" abilities is granted to that creature. If that creature loses all its abilities, it will still be removed from the game at the end of the turn, and if it would leave play, it is still removed from the game instead.
* If a creature returned to play with unearth would leave play for any reason, it's removed from the game instead -- unless the spell or ability that's causing the creature to leave play is actually trying to remove it from the game! In that case, it succeeds at removing it from the game. If it later returns the creature card to play (as Oblivion Ring or Flickerwisp might, for example), the creature card will return to play as a new object with no relation to its previous existence. The unearth effect will no longer apply to it.
The returning keyword ability, Cycling.
502.18a Cycling is an activated ability that functions only while the card with cycling is in a player's hand. "Cycling [cost]" means "[Cost], Discard this card: Draw a card."
502.18b Although the cycling ability is playable only if the card is in a player's hand, it continues to exist while the object is in play and in all other zones. Therefore objects with cycling will be affected by effects that depend on objects having one or more activated abilities.
502.18c Some cards with cycling have abilities that trigger when they're cycled. "When you cycle [this card]" means "When you discard [this card] to pay a cycling cost." These abilities trigger from the graveyard.
* Cycling is an activated ability. Effects that interact with activated abilities (such as Stifle or Rings of Brighthearth) will interact with cycling. Effects that interact with spells (such as Remove Soul or Faerie Tauntings) will not.