This Unreal Engine 5.4 video is about slowing things down, with a Sticky Mud effect.
We start by importing the Starter Content, and using a Material in it to create the Sticky Mud Niagara System. Next, we creat the Sticky Mud Gameplay Effect, which will just halve the Enemy Move Speed, per stack, but in a weird way. Then we create a function to Get Enemies in Range, and use that in the newly created Stick Mud Actor Blueprint to apply the Sticky Mud Gameplay Effect to each, every 0.5 seconds. Lastly, we elaborate on stacking Gameplay Effects and how it can go horribly wrong.
https://dev.epicgames.com/community/learning/tutorials/KPze/unreal-engine-26-sticky-mud-effect-let-s-make-a-tower-defense-game