My White Devotion Deck I made with just using Theros Block cards. This is by far my favourite deck. I love it!!
This deck has got me a lot of 1st - 3rd place standings at FNM!! However it is very weak against burn decks (Especially the current burn decks with the addition of BNG)

Breakdown of my deck:

Revoke Existence - I use this specificity to counter God cards (you can't destroy but exile works perfectly ;) ) Also great against some of the new equip cards like Gorgon's Head

Ephara's Enlightenment - My only card that has mana other than white, but for good reason. A great card to help trigger Hero abilities and and be used over and over as long as I bring a creature to the battlefield (which is not hard with the amount of creatures I have)

Ordeal of Heliod - Again, great for triggering Hero but also a quick way gain some life. By the second turn (if used on cards like Phalanx Leader or Hero of Iroas ) this card will give me life if I'm in a bad situation. Even better if I have 2 or more attached (gain 10+ life on the first attack)

Spear of Heliod - I use this not for the +1/+1 but for its creature removal ability. As long as I have 4 untapped mana, you will think twice attacking me ;)

Nykthos, Shrine to Nyx - Obvious :) Mono-white devotion = a ton of mana to cast white spells

Temple of Silence - I dont have any Temple of Enlightenment so I use this instead for the white mana. I use this just for the scry 1 ability.

Acolyte's Reward - An unbelievable white card. Not only prevents damage but can redirect back to your opponent! This could potentially cause lethal damage on the opponents turn. Why say no?

Glimpse the Sun God - When I first saw this I thought "This will go great with my Azorius Deck." Then it hit me "Tap X Creatures" any creatures....my creatures...with heroic :D. Simple - tap to attack > before opponent declares blockers cast Glimpse the Sun God > tap enough mana to tap his creatures and then cast onto my attacking heroic creatures. Since they are tapped because of tapping, the card does nothing...but!!! they were targeted so their heroic kicks in > Brilliant tactic :D

Archetype of Courage - Simple. I want First strike....Only me :P

Brimaz, King of Oreskos - I still can't find a use for this awesome feline, but he is in my deck for the fact that its a 3/4 for 3 drop and that he has good devotion

Eidolon of Countless Battles - By far the BEST Nyx card in the set...actually in the entire block IMO. For just 4 mana (2 if I have 2 Hero of Iroas on the field) my creatures not only get triggered for heroic, but it pumps up every time another creature and/or aura comes onto the battlefield...Even by itself its amazing. Its obvious weakness is if there are no creatures or aura on the field, but I intend to use this card as a Aura and not a creature.

Evangel of Heliod - I use this in case I'm running low on creature or if I REALLLLY want to pump up Eidolon of Countless Battles . My fav combo...ish move is: Fabled Hero > Bestow Eidolon of Countless Battles > summon Evangel of Heliod (Only works if I have a lot of devotion...which in this deck is like maybe 4 cards on the field)

Fabled Hero - Double Strike + Heroic +1/+1 = Holy Shnikies!! As stated above, that combo could possibly cause lethal! I love this card

Heliod, God of the Sun - There really is no use for Heliod in this deck, but I put it in just for the fact that it can pump out a creature to help Eidolon of Countless Battles pump up.

Hero of Iroas - Let's be real...It's Hercules. I say it everytime I summon him "Tap 2 mana to summon Hercules" :P. If I have 2 on the field, Eidolon of Countless Battles will only cost 2 mana to bestow...2....TWO!! That could potentially pump up a creature by 3-5.... :O

Phalanx Leader - This card should be in every white deck. It pumps up EVERYONE if triggered. Needless to say, if I have all 4 and use Glimpse the Sun God on all 4, all creatures get +4/+4...No burn spell for me today hehe