Spiked Slime

Type	Slime
Environment	Forest Slime Rain
AI Type	Slime AI
Damage	28›50›74/42›75›111 (contact); 3654 (Slime Spike)
Max Life	100›220›330/150›330›495
Defense	5›10›15
KB Resist	10%/20%
Immune to
Coins	Pre-Hardmode: 1 SCHardmode: 1 SC60 CCPost-Plantera: 2 SC40 CC
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_154.wav

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

Expert and Master Mode-Only Content: This information applies only to Expert Mode, Master Mode, and worlds with these modes.

The Spiked Slime is a slime summoned by King Slime in Expert Mode alongside Blue Slimes, becoming more common as the boss loses health. Like the Spiked Ice Slime and Spiked Jungle Slime, it has the ability to shoot spike projectiles at the player.

Notes

As Spiked Slimes 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.
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.
If a Spiked Slime is spawned in a Classic world (e.g. via third-party tools), it will have 50 health (instead of 100), even though it can never be encountered in Classic Mode normally.