For explanation, '{0}' is used for Extortion (for the Dalaran Heist's Madam Goya boss fight), which, in this case, indicates the name of the spell you transformed into a Soul Fragment.

She tries to fill the void that Shadow Word: Horror has left.

It's extreme deck-thinning, but also at an extreme price (you won't have any spells). You can go two directions from this:

1) Try to kill your opponent as quickly as possible with just a few very aggressive minions. (Priest is historically bad at this.)

2) Fill the remaining deck with high-value cards. Generate the cards you need to beat your specific matchup. (To do this you would need access to something like Archbishop Benedictus, to prevent fatigue before beating your opponent.)

First ACANIST, "If all spells are ARCANE", she is a Nightborne - an elf that was transformed by ARCANE energies.

The theme and flavour I think is on point. Lack of damaging spells from both Fire and Frost schools is quite limiting, but then you are guranteed to get value from cards like Cram Session, Shooting Star, Arcane Blast etc.

You can still Discover spells from other schools, since Mage has a lot of spell generation.

Inspired by Toad of the Wilds and our beloved Baby Kodo in Guff's story. Who don't love this baby smasher?
Harder to build than Toad of the Wilds, but reward more. This can synergy with Taunt Druid and be a good target for N'zoth.

After years of studying Arcane magic, he finally achieved a perfect form. Now, he helps other in achieving greater understanding.

Cards that work with this effect are: Devour Mind, Thoughtsteal, Seance, Madame Lazul, Shifting Shade, Drakonid Operative, Archbishop Benedictus, Mind Vision, Psionic Probe, Curious Glimmerroot, Envoy of Lazul, Soothsayer's Caravan, Chameleos, Crystalline Oracle.

Make Thief Priest not meme tier!

Battlecry: If all spells in your deck are Nature spells, equip a random weapon from your deck.

Zro K'lvin (Zero Kelvin) is a legendary Mage minion that would be released in the Forged in Barrens set to further support the direction Blizzard is pushing for Frost Mages. This also has synergy with other Frost-related cards, such as Floecaster or Frostweave Dungeoneer.

'Kind of the opposite of Shadowboxer.'

This gal can take the arcane energy from your deck to power up the gatling wand and send a minion far, far away.

Agor, Incarnate of Magic can transform into one of three forms if all spells in your deck are either Fire, Frost, or Arcane. If every spell in your deck is the same type and one of those three, it will transform into that type's respective form. This card allows you to build around it in 3 different ways, and each form has its own ability and usage.

Molten Breath and Ironforge Portal are the only current Fire spells available, but who is to say there won't be more in a future expansion? Based on the existing examples, one could assume they too would have something to do with Armor gain and/or other control elements.

[b]Rush. Deathrattle: [/b]If all spells in your deck are Fel Spells, at the end of your turn summon a Xorothian Dreadsteed.

"Information at day, in formation at night."