Lonnie Machin takes Darhk's wife and daughter hostage and Team Arrow rescues them in episode #410 "Blood Debts".
A group of satanists perform a mock-scarifice and later Lucifer and Chloe arrive to question them about the actual dead girl in episode #112 "#TeamLucifer".
Stein tries to convince Jax to join him but ends up drugging him when that doesn't work in episode #101 "Pilot, Part 1".
Backstrom and Graveley meet with the campus administration about the murder in episode #101 "Dragon Slayer".
Cheryl Blossom invites Betty, Veronica, and Archie to her afterparty where she attempts to cause havoc between the three of them in episode #101 "Chapter One: The River's Edge".