The Phoenix is another exception to this rule, as it can turn into a Cursed Hog despite spawning a Phoenix Egg on death.The Goblin Giant is an exception to this rule, as both it and its 2 Spear Goblins can be turned into Cursed Hogs.The sub-troops need to specifically be targeted and damaged/killed by Mother Witch post-spawn in order for them to spawn a Cursed Hog on death. The spawned sub-troops are not automatically cursed when they spawn from their parent troops, even if the parent troops was killed or damaged by Mother Witch.

The Battle Ram and Skeleton Barrel also cannot turn into a Cursed Hog, but the Barbarians and Skeletons which spawn after its destruction can be turned into Cursed Hogs. As such, the Cannon Cart can never get cursed since its final form is a building. Only a troop's final stage can turn into a Cursed Hog. For example, Elixir Golems, Elixir Golemites, Lava Hounds, and Golems do not turn into Cursed Hogs (they do not even show the tint of being cursed), but Elixir Blobs and Golemites do. Any troops that spawn sub-troops (smaller variants) upon death will not spawn a Cursed Hog.A Mother Witch card costs 4 Elixir to deploy. If the troop dies during the curse's duration, a Cursed Hog will spawn, which has moderate hitpoints and very low damage. When the Mother Witch attacks a troop, that troop will have a curse placed on it for 5 seconds. It spawns a single-target, air-targeting, medium-ranged, ground troop with moderate hitpoints and moderate damage.

The Mother Witch is a Legendary card that is unlocked from the Miner's Mine (Arena 15). When a cursed troop is destroyed, it turns into a building-targeting Hog that fights alongside the Mother Witch. “Places a curse on enemy troops with each attack.

Hog rider wiki