You'll need to hunt down Wurmling Bones in order to spawn Worldcarver A'tir in World of Warcraft: Dragonflight. Rare mobs are often pretty tough to take on solo, so it's not a bad idea to group up or wait until there are a few others in the area before engaging one—especially if it's your first time taking it on.
As the name suggests, rare enemies are often challenging to find and either have long spawn timers or require you to perform some action to make them appear. In the case of Worldcarver A'tir, you need to collect three Wurmling Bones, so here's where you can find them in WoW Dragonflight.
WoW Dragonflight Wurmling Bones location
The Worldcarver A'tir rare elite enemy can be found in The Waking Shores zone of the Dragon Isles. Its spawn location is on the area's west side, close to the Obsidian Citadel, where Wrathion and Sabellian (opens in new tab) reside. You need to bring three Wurmling Bones to the Wurmling Bone Pile to get it to show up, and I've marked the location on the map above.
Worldcarver Wurmlings drop Wurmling Bones, but these enemies are pretty tough, so grouping up before you get started is a good idea. The bones aren't a guaranteed drop, either, so you may have to kill a few to get the three you need. It's also worth noting that the Wurmling Bones only have a 15-minute duration, so if you don't use them within that time, they'll disappear from your inventory.
The wurmlings also have the chance to drop a Magma Core, which is needed for the Fuel for the Forge (opens in new tab) blacksmithing quest, so it's something to keep in mind if you're on that quest.
Once you've gathered three Wurmling Bones, take them to the Wurmling Bone Pile to spawn the rare elite enemy, Worldcarver A'tir. Once defeated, it can drop various crafting reagents, gear, and dragonriding customisation options. You'll also get to tick this rare off list of special encounters needed for the Adventurer of the Waking Shores achievement. Good job!