Shax was the Source's assassin. He killed Prue and her sisters vanquished him. When Coop brought Piper to the manor, he asked her about the Source sending Shax to kill Prue, if that was why she was so deturmined to take down the Source.
After learning that he is a witch with magical powers, Brent goes running down the hall with his hands ready to shoot some sparks. His apparent target is a teacher walking down the hall. When Paige orbs Brent out, the teacher must have heard something, because he looks up.
Not much is known about her other than she lived somewhere around two hundred years before Coop met Phoebe. Most likely her married name was Coopersmith, as that is the name of the present day family and her husband (or less likely she) might have been in mining, though it could have been a decendant of hers or an ancestor of either her or her husband's that was a miner. She mourned the death of her son, but it is unknown what she named him or if he was born alive or not. She may have had at least one other child who was the ancestor of the present day branch of the family, but this is not known for sure.
Henry talked with one of the fire inspector's investigating the fire at his house and convinced him to let him take a piece of evidence to show Phoebe. When he handed it to her, he told her that the investigator was a friend.
Lawrence was Charlotte Warren's fiance and lover. He was also Melinda Warren's father. Lawrence disappeared shortly before Charlotte found out that she was pregnant with Melinda. Melinda gave her mother the knowledge that he was not coming back. He is presumed to be dead at that time, but that is not known for certain. Very little is known about him.
Mitchell Coopersmith's parents. They do not agree on the family tradition of having a cake shaped like the Old Coopersmith Mine at every major family function. Mrs. Coopersmith accused her husband of ruining their wedding by having it there. Their fighting escalated at the wedding and when the Charmed Ones were trying to fix things, Paige went to deal with them and try to calm them down.
Senator Holcombe and his wife are Bree Holcombe's parents. This was the reason Elise Rothman wanted Phoebe to do a report on the wedding of the Bree and her fiance. It was also the reason Piper was excited when she found out she was hosting the rehearsal dinner. It was not officially confirmed that Bree's parents were the people seated next to her on her left at the table, but it's likely as Mitchell's parents were seated next to him on his right.
When Paige went to the beyond, she was met by Grams and Patty first, but then, they lead her to where they had gathered a great deal of help in the form of many Warren witches. Melinda Warren led the group and greeted Paige.