Pendulum Summon

A Pendulum Summon (Japanese ペンデュラム Pendyuramu Shōkan, abbreviated in card text) is a form of Special Summon introduced in Yu-Gi-Oh! ARC-V. Pendulum Summoning allows the player to Summon multiple monsters simultaneously.

Mechanics
Once per turn, during the Main Phase, if the turn player has a Pendulum Monster in each of their two Pendulum Zones, the turn player can Pendulum Summon any number of monsters from their hand and/or any number of Pendulum Monsters that are face-up in their Extra Deck with a Level or Rank between the blue Pendulum Scale of the Pendulum Monster in the left Pendulum Zone and the red Pendulum Scale of the Pendulum Monster in the right Pendulum Zone, exclusively.

Because only monsters with Levels between the Pendulum Scales of the Pendulum Monsters can be Pendulum Summoned, no monsters can be Pendulum Summoned if the Pendulum Scales of the two Pendulum Monsters are equal or are 1 apart (however, this does not prevent the usage of the Pendulum Monsters' Pendulum Effects).

A Pendulum Summon is a type of built-in Special Summon, so it can be negated—cards like "Solemn Warning" and "Thunder King Rai-Oh" that can negate Special Summons can be activated during the Summon negation window; however, if more than 1 monster would be Pendulum Summoned at the same time, cards like "Thunder King Rai-Oh" that specify they can only be activated when exactly 1 monster would be Summoned cannot be activated. After a Pendulum Summon is successfully performed, cards such as "Bottomless Trap Hole" can be activated during the Summon response window. A Pendulum Summon is not the effect of the Pendulum Monsters in the Pendulum Zones, so can be performed even if "Spell Canceller" is on the field, and does not use a Chain Link.

In the anime
When a Pendulum Summon is performed in the anime, a portal opens between the two Pendulum Zones and streaks of light emerge from these zones, representing the monsters. The color of the light streaks appears to depend on the number of monsters that are being Summoned; three monsters for example results in a green, blue and a red streak, while two results in a green and a blue streak. On occasion however the energy changes; Declan's monsters vary between a surge of purple light or purple streaks; while "Mayosenju Daibak" appears from the portal in the form of a green tornado. In addition, Yuya Sakaki's Pendulum Summons have an enlarged version of his pendant swinging between the zones.