Runeforging is a skill exclusive to Death Knights, which consists in enhancing your weapon. I decided to implement this in the form of buff spells that can target both weapons or minions.

Besides some collectible Runes, there are three basic ones, akin to Shaman's basic Totems. These are not collectible and can be generated by several cards, with Razuvious being one of them.

Keep in mind the Frost Rune lasts forever, while the other two are one turn only. Not all keywords are created equal, after all!

Lord Marrowgar uses the idea of a potential self-freeze archetype for Death Knight that would use freezing effects to enpower both your mininos and your hero. In this case, the idea explored is allied characters frozen in ice becoming more resistant to enemy threats.

'Why is it called Invincible if it doesn't have Stealth?'

Since Paladins excel at handbuffing, I thought Death Knights could excel at debuffing your opponent's hand.

If a minion in your hand is reduced to 0 Health by this effect, I imagine that when you play it, the battlecry will trigger and then the minion will immediately be destroyed.

Lord Tamakeen epitomizes the Death Knight's oft-overlooked "Blood specialization" in WoW, which focuses on tanking via Health regeneration and Lifesteal. Gaining Armor instead of Health allows you to "overheal" past your regular life total, much like the Warrior does. It could also help you stay healthy while keeping your damaged state "low" for effects such as Lokholar the Ice Lord.

Not much to say, I just thought a bit about what the "giant" for DK would possibly look like. 

Considering this would be a new class, the power level of the cards should be on par with what we saw released on day 1 with DH, with a +1 added for good measure. Better have a card that sees lots of play and says it was overpowered later, rather than have a card that sees no play and needs help to get it played. 

I believe the base stats and additional features are adequate for the requirements needed to make the card viable. A 0 mana 8/8 that can heal, and possibly attack right after coming into play might look scary, but with how the meta has shifted to more board-centric games, and removal is everywhere you look, it's hard to see Cristole as a game-breaker. 

Teribus the Cursed is the Legendary Dragon to go with Death Knight's Initiate set, to mirror Demon Hunter getting Nethrandamus.

Like Nethrandamus, Teribus also interacts with dead minions (we are Death Knights after all, that's kinda their thing), drawing on the power of your highest-Cost friendly minion that died this game. For example, if the highest Cost of dead friendly minions that game is 6, Teribus will deal 6 damage to all other minions (and the card has a counter that keeps track of this).

Teribus can work really nicely in a Death Knight deck that uses a lot of big minions, but he's also a really good for Dragon Death Knight too, being both a Dragon himself and taking advantage of the fact that many powerful Dragons are naturally quite large.

I like the idea of Death Knight having effects that Freeze a friendly minion or powerful minions that Freeze themselves when played or under specific circumstances.

You could sacrifice Yallesh to a minion and he would simply come back as long as you can get a Frozen minion on the board. Freezes only last one turn, so you'll need plenty of synergy to keep Yallesh 'sticky'.

Death Knight would likely be a more control focused class, so if you want to go face, you'll give the opponent an easy opportunity to remove it, provided they can take care of any Frozen minions first.

A basic legendary to synergize with Death Knight's use of weapons (Frostmourne) and existing self-damage identity (Obliterate), offering a powerful stabilization and sustain tool for Control strategies. 

"You know what they say, the best never  rests."

I imagine that if Death Knight were ever to come out, it'd try having a self-mill archetype with cards like Keening Banshee or Fel Reaver, Doom Pact and Army of the Dead. I made the Legendary a bit stronger intentionally since they don't have as much cards as the other classes (especially ones for a self-mill archetype).

Deathknights would use Frost spells to Freeze minions, bolster their weapons or gain armor and occasionally drawing cards or summoning minions.

Lady Deathwhisper lets you turn some of that armor you have gained throughout the game into Mana... but only for other Frost spells!

Inspired from Vryghoul, Arrogant Crusader, and Skelemancer.

This card plays with the theme of stealing your opponents stuff like with the original Death Grip card. This card plus obliterate can steal some of your opponents stuff for pretty cheap, or if you have ways to reduce your mana, this card plus Death and Decay steals your opponents small minions. Overall more meant for fun and flashiness over actually being competitive.