Arachnopocalypse

You summon 1d100 fey spirits that take the form of spiders and appear in unoccupied spaces that you can see within range.
Roll 1d6 to determine the size and amount of creatures summoned:

1. Tiny
2. Small
3. Medium
4. Large
5. Huge
6. Gigantic

Each spider is considered a fey, and it disappears when it drops to 0 hit points or when the spell ends.

Roll initiative for the spiders, which have their own turns. When you summon them and on each of your turns thereafter, you can issue a verbal command to them (requiring no action on your part), telling them what they must do on their next turn. If you issue no command, they spend their turn attacking any creature within reach that has attacked it.

At the end of each of the spiders' turns, make a DC 16 Charisma saving throw. On a successful save, the spiders continue to obey you. On a failed save, your control of the spiders ends for the rest of the duration, and the spiders spend their turns pursuing and attacking the nearest non-spiders to the best of their ability. If you stop concentrating on the spell before it reaches its full duration, the uncontrolled spiders don't disappear for 1d6 rounds if they still have hit points.