The current two "Pendulumgraph" cards, "Time Pendulumgraph" and "Star Pendulumgraph", prevent the opponent from targeting your Spellcaster monsters with Trap and Spell effects respectively. In addition, the first enables destruction of both opposing cards and your own "Magician" Pendulum monsters, while the second lets you search for other "Magicians" from your deck whenever those get destroyed.
"Purple Poison Magician", "Black Fang Magician" and "Double Iris Magician" work well with "Pendulumgraph" cards, as their effects activate whenever they are destroyed, with "Iris" searches for the two cards. "Sky Iris" has good synergy with decks utilizing those cards.
As per the New Master Rule, the use of both "Pendulumgraphs" at a time, especialy within "Pendulum Magician" deck, will cause the player to have problem using Spell and Trap cards. Plan wisely before one set a card.