Patch 8.3: Visions of N'Zoth mounts
Patch 8.3: Visions of N'Zoth introduces at least 26 new mounts to collect. While there are no new zones to explore, there are new 'Assault' phases of Uldum and the Vale of Eternal Blossoms, as well as Horrific Visions instances. In addition, the new raid: 'Ny'alotha, the Waking City', and the new pvp season: BfA Season 4 both commence two weeks after patch launch (though the Arena mount won't be awarded until the end of the season.)
Matching Companion Pets
Blizzard Shop / Promotions / Trading Card Game - Other Mounts
The icy-blue Rajani Warserpent is sold by Zhang Ku in the Vale of Eternal Blossoms for one Pristine Cloud Serpent Scale. We don't yet know where the scale comes from, but hopefully someone will report it soon!
Loot - Miscellaneous Scenario and Instance Drops
The creepy Mail Muncher drops from an NPC of the same name. It can be found in Horrific Visions scenarios added in Patch 8.3. See Wowhead's Horrific Visions Guide for more information.
Loot - Raid Boss Drops
Coming soon - the Ny'alotha raid will launch two weeks after the release of Patch 8.2. The many-eyed Ny'alotha Allseer drops from N'Zoth, the Corruptor in the raid 'Ny'alotha, the Waking City' on Mythic difficulty only. As with previous Mythic raid mounts, it is likely that the Ny'alotha Allseer will be a guaranteed drop (for all party members) at the time the raid is current, but it'll become a rare drop once the next expansion is released. Note that although Mythic difficulty has been removed from the Allseer's description in the mount journal - which might suggest it drops from other difficulties - it's still only listed among Mythic loot in the Adventure Guide. We'll have to wait and see.
Loot - World Boss or Rare Drops
At least eight new mounts drop from rare spawns introduced in Patch 8.3. Seven of these are in the new Assault phases of Uldum and the Vale of Eternal Blossoms. One more (Mollie) apparently drops from an older world boss - Dunegorger Kraulok in Vol'dun.
Quests & Exploration - Ahead of the Curve
It is likely that this impressive void dragon will be the Ahead of the Curve reward for the final patch of Battle for Azeroth. N'Zoth will likely drop a Spawn of Vexiona quest item for every victor on Heroic difficulty or above, which will trigger a quest leading to the mount. This will almost certainly be removed once the Shadowlands expansion launches.
Quests & Exploration - Mount Quest Chains
You can earn this fanciful, tentacled insect mount by raising it from a newly-hatched drone. The quest chain begins by locating a clutch of Voidtouched Eggs near Ankhaten Harbor in Uldum and the entire chain takes 30 days. See this Wowhead comment if you want a day-by-day description.
Quests & Exploration - Special Activities
Two alpaca mounts may be obtained through special feeding activities. The sooty Elusive Quickhoof only seems to require a one-off interaction with a rare NPC of the same name in Vol'dun, while the golden Springfur Alpaca requires you to locate and feed Friendly Alpacas around Uldum for seven days.
The Uldum Accord - a new faction in Patch 8.3 - sells this dark crimson vulture mount at Exalted.
Player / Racial Factions - Alliance Allied Races
This nifty new mechanostrider is the racial mount of the Mechagnome allied race, though it is usable by all Alliance players on your account. You receive this mount when you unlock the Mechagnome allied race by recruiting them to the Alliance.
Player / Racial Factions - Horde Allied Races
This handsome hyena is the racial mount of the Vulpera allied race, though it is usable by all Horde players on your account. You receive this mount when you unlock the Vulpera allied race by recruiting them to the Horde. Its canopy can be attached or removed by interacting with a Caravaneer's Pack at a Vulpera camp, which is created by the Vulpera racial ability Make Camp.
Player vs Player - Arena
Coming soon - BfA Season 4 will launch two weeks after the release of Patch 8.3. The Gladiator's mount reward for BfA Season 4 will be this swarthy Proto-Drake. Like all Arena mounts, it won't be available until the end of the season.
Player vs Player - Vicious Mounts - Rated PvP
The rated PvP ('Vicious') rewards for BfA Season 2 have a white theme. To earn one of these handsome mounts, players must first reach the PvP rank of 'Combatant' during the season by reaching a rating of 1400 from competing in 2v2, 3v3, or 10v10 arenas and battlegrounds. They must then win a further 100 rated PvP matches during the season.
Achievements - Dungeon Keystone & Challenge Modes
Previous expansions have offered a mount for dungeon Challenge Mode achievements. Instead in BfA we can earn this grey serpent of N'zoth for completing all Battle for Azeroth Season Four dungeons at Mythic Level 15 or higher, within the time limit. This will possibly be much more difficult than previous expansions, but time will tell.
Achievements - Miscellaneous Scenario and Instance Achievements
Achievements - Raid Meta-Achievements
Coming soon - the Ny'alotha raid will launch two weeks after the release of Patch 8.2. This purple serpent of N'zoth is the reward for completing Glory of the Ny'alotha Raider - the raid meta-achievement for the 'Ny'alotha, the Waking City' raid on Normal difficulty and above.
Expansion Features - Horrific Visions
The sinister red Wicked Swarmer is sold by Wrathion in the Chamber of Heart, for 100000 Corrupted Mementos which can be earned by running Horrific Visions scenarios. Wowhead has a detailed guide on how to earn these.
Expansion Features - Service Medals
Service Medals were introduced in BfA as a currency for Warfront-related activities. The introduction of a new vendor mount, the Sandy Nightsaber, coincides with the release of Heroic Battle for Darkshore in Patch 8.3. It costs 350 7th Legion/Honorbound Service Medals, but only available after you've completed the Heroic Battle for Darkshore.
Unavailable New Looks
Unavailable New Looks
Two more alpaca colours were added to the database in Patch 8.3, but aren't yet available as mounts. Perhaps they'll appear at a later date. Unfortunately the red alpaca colour hasn't been turned into a mount yet.