Pendulum monsters in the game of Yu-GI-OH is as followed, they are very recent addition to the game beginning in the year 2014. There mechanic is as followed, these monsters are not just monster they are both consider a spell card and a monster rolled into one card. So, they have two text box's one being called the monster effect and the over being called the Pendulum effect. Now know this a Pendulum monster that has no monster effect but does have a Pendulum effect is still considering a normal monster. The Pendulum effect can as be anything that is within the context of the card game of Yu-GI-OH. To use them in a game you will put them into the far left and far right of the spell/traps card zone this is what's called set up the scales. This means this take for example the example card Performapal Skullcrobat Joker with has two scales levels of 8 setting this card on the left most column in the spell/trap card zone and the cannon card on the right most spell/trap card column then you set up the scale. When the scales are set up then taking the number in-between the 8 - 2 of those Pendulum monsters (this being level 7-3) you can special summon anyone of those level from your hand or extra deck to the field one time. This is what is known as a Pendulum summon. Pendulum monsters also have a very special action, and that is when a Pendulum monster is destroyed. When a Pendulum monster gets destroyed unless by certain effects such as being banished, they are sent into the extra deck faceup. Therefore, a Pendulum summon can summon from the extra deck if you met the scales. Also, Pendulum monsters act as continues spell cards while on the field so any cards that effect spells cards with also effect the Pendulum monsters while in the Pendulum zone.