Spiked Slime

Type	Slime
Environment	Forest Slime Rain
AI Type	Slime AI
Damage	28›50›74/42›75›111 (melee); 3654 (ranged)
Max Life	100›220›330/150›330›495
Defense	5›10›15
KB Resist	10%/20%
Immune to
Coins	Pre-Hardmode: 1Hardmode: 160Post-Plantera: 240
Hurt	https://terraria.wiki.gg/wiki/File:NPC_Hit_1.wav
Killed	https://terraria.wiki.gg/wiki/File:NPC_Killed_1.wav
Slime Spike	https://terraria.wiki.gg/wiki/File:Item_17.wav

Expert Mode-Only Content: This information applies only to Expert Mode and Expert Mode worlds.

Desktop/Console/Mobile-Only Content: This information applies only to the Desktop, Console, and Mobile versions of Terraria.

The Spiked Slime is an enemy summoned by King Slime in Expert Mode. Spiked Slimes are summoned alongside Blue Slimes by King Slime and become more common as the boss loses health. Like Spiked Ice Slimes and Spiked Jungle Slimes, they have the ability to shoot spikes at the player.

Notes

As they are exclusively found as part of the fight with King Slime, they are similarly unaffected by the immunity granted by the Royal Gel and will continue to fire projectiles and damage the player on contact.
Although it is normally impossible to encounter a Spiked Slime on its own, it will have 50 HP instead of 100 if it spawns alone.
Defeating a Spiked Slime is not required for the Gelatin World Tour achievement.

Their spikes seem to be made out of hardened gel.
The Spiked Slime, Baby Slime, Slimeling, Crystal Slime, Heavenly Slime, Golden Slime, and Bouncy Slime are the only slimes without their own banner.
While other enemies spawned by bosses, such as the Servants of Cthulhu, have a Bestiary entry, the Spiked Slime does not. This is likely because it is an Expert Mode-exclusive enemy and if it did have a Bestiary entry, it would be impossible to complete it fully in a Classic world.
The Spiked Slime, Jungle Mimic, Golden Slime, and Pirate's Curse are the only killable enemies without Bestiary entries.