Grease in 5e states that a character who fails a DEX save goes prone. It takes half their movement to get up. If a character can move 30 feet/round – then the character can exit the greased area because the greased area is just a 10 feet square.
Does that effectively mean that the most amount of time any character or creature will typically be caught is one round?
OR…does that character have to roll again if they enter another 5 foot square of grease?