According to senior game designer Mike Donais the Hearthstone development team doesn't plan on ever releasing more cards to support C'Thun. Whispers of the Old Gods launched with about 17 cultists and that's all players will have to work with as the card carries out its Standard lifespan before moving into the depths of Wild.

C'Thun, one of the four Old Gods released in the set, is given to all players who buy a single pack of the set. It's seen a good amount of success, even helping Handsomeguy win the Asia-Pacific Spring Championships this past weekend. Though it's undoubtedly competitive, it's not automatically considered a must include in any decks or competitive lineups, but is extremely solid in decks that are built around it, something that was hard for the development team to nail.

"Balancing the card was a challenge," Donais tells IGN. "If we miss by a little bit then the C’Thun mechanic is a total wash. And we’re done, because we’re not ever going to add another C’Thun card, so it’s a big mess. And if we miss by a little bit in the other direction, you play C’Thun and he does 30 damage to your face. He’s too powerful, right? It’s a big risk trying to get C’Thun exactly at the right level."

At some point the team realized that the number of cards dedicated to our large eyeballed friend was incredibly important. Citing Goblins vs. Gnome's mech problem - having an entire set defined by only a fraction of the cards it contains - a few cards had to get reworked.
" Cult Apothecary used to be a C’Thun card… that healed based on your C’Thun stuff," says game designer Peter Whalen. "There was just a little bit too much C’Thun stuff. The way it’s turned out it looks perfect – Mike did an amazing job – but that’s one of the tuning things that we did."

But a few were just outright eliminated, "We did one that did one damage in many packets based off C’Thun stuff," reveals Donais. Whalen continues, "It was an actual mini C’Thun, which shot Arcane Missiles based on C’Thun." The conversation bounces back to Donais. "Yeah, something like that. It was a bit more complicated because the mechanic was slightly different, but basically it did one missile for each cultist you played that game, or something like that." "Died that game," Whalen interjects.
  • The interview also mentions that Hunter had a "make C'Thun cheaper" card at one point.
  • Twin Emperor Vek'lor activated off of the Reno effect rather than C'Thun.
  • Before Blizzard settled on the final design, Yogg-Saron, Hope's End read "replay every spell you played this game."
N'Zoth, the Corruptor is probably the most widely accepted Old God. Players can simply insert him into a deck that already has a lot of Deathrattles and get considerable value out of just those few minions. This is something that Blizzard admits will inhibit the strength of cards with that keyword in the future.

"It constrains deathrattle taunts a little bit," Whalen confesses. "I’d say, though, that the obvious counter-play to N’Zoth is just – kill the guy. If his plan is to play a 10 mana guy and get a bunch of minions that don’t have taunt, just kill him. That’s a reasonable plan."

Donais backs him up, "He does make us think about deathrattles. As we were going into shipping the set we were like, well, from now on we’re going to have to think about every deathrattle, learn about how good N’Zoth really is in the real world – because we never know for sure – and if he’s the thing that everyone’s complaining about, then we don’t put a lot of good deathrattles out for a while. And, y’know, maybe we should have some counter-play cards – we don’t know yet, but we’ll look at it, see if we can create some counter-play cards. Think Polymorph and Hex."

For more information, check out the full IGN interview.