Last night in my session, a wizard and I stopped a small group of pursuers chasing our wagon with a timed Grease and Web spell cast at the same time. With the group failing at least one of the saves, it turned the potential combat into just straight up negotiations.
Not every encounter may be ended directly by this though so I'm curious how these two spells interact with someone failing at least one and in the intersections of the two spells. Once caught in a greasy web, how hard is it to get out and what/how many successful or additional saves need to be made? Being restrained and prone seems to leave very little options and with the spell saves needing to be repeated at certain points it seems like the checks compound quickly.
For simplicity, I'll also put the spell descriptions below:
You conjure a mass of thick, sticky webbing at a point of your choice within range. The webs fill a 20-foot cube from that point for the Duration. The webs are Difficult Terrain and lightly obscure their area.
If the webs aren't anchored between two solid masses (such as walls or trees) or layered across a floor, wall, or ceiling, the conjured web collapses on itself, and the spell ends at the start of your next turn. Webs layered over a flat surface have a depth of 5 feet.
Each creature that starts its turn in the webs or that enters them during its turn must make a Dexterity saving throw. On a failed save, the creature is Restrained as long as it remains in the webs or until it breaks free.
A creature Restrained by the webs can use its Actions to make a Strength check against your spell save DC. If it succeeds, it is no longer Restrained.
The webs are flammable. Any 5-foot cube of webs exposed to fire burns away in 1 round, dealing 2d4 fire damage to any creature that starts its turn in the fire.
Slick grease covers the ground in a 10-foot square centered on a point within range and turns it into Difficult Terrain for the Duration.
When the grease appears, each creature standing in its area must succeed on a Dexterity saving throw or fall prone. A creature that enters the area or ends its turn there must also succeed on a Dexterity saving throw or fall prone.