Shadowmere

Shadowmere was the horse of Nathan Loan, as well as his first pet in Minecraft.

Early life
Not much is known about Shadowmere before his first appearance.

Nathan's House Tour V2
Nathan introduces Shadowmere to Chris, but Shadowmere does not like being around Chris.

Mini-Golf
During Nathan's first appearance in Deep Sheep: Season 2, Nathan rides Shadowmere into Fudge Pantz Pen in Chris's Forest. Chris at first tells Nathan to get out, but soon gets distracted when Camden fires chicken eggs at Chris's trophy wall. As Nathan continues to ride Shadowmere, he is kicked from the game, along with everyone else.

Combat Evolved
Chris flies over to The Krusty Krab and notices Shadowmere wandering behind the restaurant. Nathan, who had been wondering where Shadowmere was, goes to find Chris.

Chris rides Shadowmere back to the stables, with Nathan, Camden, and Spencer not far behind. Chris gloats that Shadowmere likes him, and asks Nathan if he can keep him. Nathan threateningly pulls out a bow, aims toward Chris, and utters, "Get off Shadowmere."

Everyone meets up at the Snake Sniper Tunnels, where they come across 2 skeleton horses, one of them claimed by Alaxx. Nathan wants the other one so that he can name him Arvak, after another horse from Skyrim, and complete the pair of Shadowmere and Arvak. He also creates the idea that whoever wins the episode gets the horse.

Death
In the end, Nathan's team ends up winning, and Nathan victoriously mounts Shadowmere. As he does this, Chris and Robby, bitter over their defeat, barrage Nathan and Shadowmere with splash potions of harming. One of Robby's potions is the one that kills Shadowmere.

Chris flies down to a shocked Nathan and tells him that "was for Oreo." Oreo was a horse Chris befriended in Mini-Golf, and was eventually killed.

Camden stands up for Nathan, as he was the one that killed Oreo, not Nathan. Nathan tells Camden to get out of the way and ominously tells Chris and Robby that they will pay for what they've done.

Shadowmere is buried in the Deep Sheep Cemetery in Fudge Pantz' Corner.

The Iron Chef: Part 1
Everyone looks at Nathan's shrine for Arvak, as one of the 4 Horses of the Apocalypse. Chris arrives and gloats that Nathan only has 1 horse, which is "how it should always be". Nathan ominously replies, "You're still gonna pay for that".

Skin Town Tour: Season 2.5
During the tour, Spencer, Connor, and Chris reveal the newly-revamped Deep Sheep Cemetery, where Shadowmere was interred. Chris says to Shadowmere's grave that Shadowmere was his least favorite horse, and that he is not sad at all about Shadowmere's death.

Cover Fire
After Nathan and Alaxx win, Nathan announces that he would like to say something, originally directing what he has to say towards Chris and Robby for killing Shadowmere, and then, after a few more episodes, he decided to direct what he has to say towards everyone except his teammate Alaxx.

He announces, "Anyway, guys, I just want to say, fuck you (to Chris), fuck you (to Robby), fuck you (to Spencer), fuck you (to Camden); Alaxx, you're cool. I've been putting up with your guys's bullshit for so long." Everyone went wild over this, as this was the first ever time that Nathan swore, especially while on camera. Amongst everyone's screaming of shock and excitement, Robby says "RIP Shadowmere, fucking worth it."

Defend and Conquer: Part 2
In Defend and Conquer: Part 2, before the final battle begins, Camden and Chris enter the End by jumping through the End Portal at Halloween Hill. While there, they come across all of the dead pets from both seasons, including Shadowmere, and release them into the Overworld.

Shadowmere is the first one to return, after one of Alaxx's Shulkers strikes him, and sends him flying. When the effect wears off, Shadowmere plummets into the portal to the Overworld.

Trouble in Skin Town
Shadowmere makes one last appearance, in the Season 2 Finale, at the Deep Sheep Cemetery, along with all the other dead pets, on their second leash of life.

Trivia

 * Nathan has no pets in real life.
 * Shadowmere is a black horse.
 * Shadowmere is named after a horse in Skyrim, Nathan's favorite game.
 * Nathan's other horse Arvak is also named after a horse in Skyrim.
 * It is believed that Nathan got his revenge on Chris for killing Shadowmere: In the Defend and Conquer: Part 2, most of the Biome Tree is obliterated by an enormous stockpile of TNT. This was revealed to be a plan devised by Robby, which he showed to Chris and Alaxx. A lot of people in the comments section of that video believe that Nathan was in on that plan too, and ultimately got his revenge by doing so.