Hero: Gravebone (41 cards)

Ally (22):
4x Popsickle
3x Death Mage Thaddeus
3x Cryptspawn Tormentor
4x Falseblood Cultist
3x Stalactitan
4x Forgotten Horror
1x Dakrath

Ability (13):
4x Sacrificial Lamb
2x Suspended Animation
4x Shadowbolt
2x Supernova
1x Widespread Decay

Item (5):
1x Leash of Life
4x Living Ice Wall

Deck Code: 842674B

I started this deck with Eladwen and Popsickle, having in mind full on thematic freeze deck, but that one felt a bit too janky, although very fun when it works. Based on advice from Telegram SE group I switched to GB and slowly the deck morphed into variation of Undead GB.
Playstyles are very similar. Many matches you win with spamming Horrors from hand and via GBs ability. Compared to pure Undead GB you have few more tricks up your sleeves though.
Horror is quite a glass cannon with 4 hp so Living Ice Wall comes in to protects it. You also have alternative win conditions with Popsickle and Stalactitan. Beyond just freezing allies with Horror and buffing Popsie's and Stalactitan's attack, they also get buffed and protected from Living Ice Wall. On top of being aggressors they provide some control tools via their active abilities. And speaking of flexible control and aggression, Suspended Animation can provide both as well. For example, you can return an ally from GY with GB ability and use SA to protect it. Or, you can death race opponent by freezing their board and attacking hero with buffed Popsickle and Stalactitan. These are the key cards to deck's strategy. Remaining ones provide tech, draw and support.
Cultist is staple in GB to cheat in Horror or Dakrath early and later in the game to cycle your hand. You don't have to go super high on resources and 7 resources is the top end, while deck works at 6 just fine.
Sac Lamb is 4 off instead of having dedicated draw engine because it is much more tempo efficient and it has nice synergy with the undead, especially Tormentor. Sometimes opponent will try to disable Horror instead of killing it in an effort to prevent GB from returning it from GY, and SL is very efficient in that case as well.
Shadowbolt should IMO become staple in any undead GB. It is not as good as Shadow Font in SE ramp, but board control option more than makes up for that.
Supernova is there in case things get out of hand and opponent spams the board with allies.
Widepsread Decay is item tech choice because I don't have room for multiple item removal and this is kinda the most universal one, even though it doesn't excel in weapon/armor removal.
Leash of Life as 1 off is neat if you draw it. Makes it easier to use Popsie's and Stalactitan's abilities and can sometimes surprise warriors, but it is not necessary.