Only three of you entered? We expected more. Three are easy to deal with.
ZEL is one of the admins of Team Meteor. An amalgamation of three different personalities, namely Zero, Eve and Lumi, ZEL develops PULSE Machines for Team Meteor.
Zero is the most aggressive personality, acting harsh to others and even their other personalities. Eve is the smartest personality, developing PULSE machines entirely on their own, and possessing a great understanding of Pokémon's abilities. Lumi is the kindest of the three, cheering on the Tangrowth in the PULSE Machine despite all the damage it causes, encouraging Eve, and attempting to be friendly and polite to the player. She also gets angry at Zero constantly for yelling at Eve about the PULSE machines.
ZEL first introduces themselves at Obsidia Park, in front of a mass of metal and flora that has ensnared Amaria and Florinia. ZEL at first appears to be arguing with an unseen accomplice, but as the conversation continues, it is made clear that ZEL has three distinct personalities: Zero (dialogue presented as Zel), Eve (dialogue presented as zEl), and Lumi (dialogue presented as zeL).
After the defeat/death of the PULSE Tangrowth, Zero and Eve argue with each other over Zero's error in using the PULSE Tangrowth for battle, while Lumi apologizes to it for not stopping them.
ZEL is encountered again in the Beryl Ward with Taka and a mysterious agent, irritated with the player's interference. After Heather's interruption, the agent commands them to team up with Taka against the player. After their defeat, Eve gives a frank analysis of the situation and determines there is no use in their staying, and Lumi's nervousness guides the trio to follow Taka.
ZEL later reappears in Blacksteam Factory, where they are monitoring the PULSE Muk along with Solaris. The PULSE Muk is responsible for poisoning Azurine Lake, and ZEL tries to stop the player from defeating it. After the battle, PULSE Muk disappears and Team Meteor makes a retreat due to the lake already being poisoned.
When the player raids the Tanzan Meteor Base, ZEL appears to have trouble stabilizing PULSE Abra. Lumi was hoping to ask Abra nicely to teleport them inside the gate underneath the Grand Stairway but Zero replies that its not listening. Abra's amplified teleportation powers is why Spinel Town is in disarray. The player and Saphira try to stop them but gets teleported instead to Tanzan Depths.
The player later comes back to the Tanzan Meteor Base only to find ZEL being teleported around by Abra. Due to Abra uncooperating with Team Meteor, Eve suggest to simply terminate the project, which Zero agrees. Lumi however is against it, but Eve says Lin is coming soon and this would be unacceptable to present, and would stop anymore teleportation accidents from happening further. ZEL then decide to battle the player to terminate Abra. After Abra is terminated, the player is let go by Sirius in the hopes that they never meet again.
This article contains plot details about events that occur later in the game.
A diary discovered in Ametrine City reveals the history behind this odd character- ZEL truly is three people in one body, fused together as the result of a PULSE Machine attached to a Magneton that evolved into a Magnezone while it was still hooked up. Evelyn Seijaya, the original identity of Eve, had developed the machine in an attempt to heal her sister, Luminia Seijaya, the original identity of Lumi, hoping to keep her from dying. Zero, a member of Team Meteor, somehow learned of Evelyn's project, and attempted to force her into giving the power behind it to the organization. Luminia, sickly and frightened, simply feared death and being alone. As the great accident occurred, all three of them got what they wanted, but in a terrible manner.
After the protagonist, Victoria, Arclight, Adrienn, and Ame are all captured by Team Meteor during the attempted raid on a Meteor facilty hidden in Devon Corp and transported to a hidden base elsewhere in the city, ZEL stayed behind after the base was evacuated, due to an unknown source inserting a corrupted program into the data of the PULSE that empowered the Magnezone responsible for turning them into ZEL. They are encountered a final time in the chamber containing said PULSE Magnezone, where, after questioning if the "heroes brigade" planned to destroy everything there, ZEL engages them in battle with their full team, including the PULSE Magnezone.
However, after Magnezone is defeated, Lumi and Eve are seemingly expelled from Zero's body, leaving him alone for the first time since the accident and horrified by the loss of his comrades, and leaves for Agate City afterwards.
Zero is later found with Bennett in the Glass Factory, controlling the PULSE-Hypno responsible for Agate City's sleepy veil. He talks to the player like if Eve and Lumi were still inside him, indicating he might suffer from schizophrenia. He reveals that PULSE-Hypno was mentally controlling Cain and Shelly, and command them to battle the player. After the latter wins, Bennett tells Zero to let Shelly go, only to take control of the player instead.
After the player escapes Gardevoir's black hole, Radomus explains what happened while the player was under the PULSE-Hypno's control. After Gardevoir used the black hole in order to protect Radomus, Zero and Bennett argued over what happened, and Bennett says Zero is a high-ranked Team Meteor member only thanks to Eve and Lumi, as he was a simple grunt before the Magneton/Magnezone event. Zero is told by Bennett to report the events of what happened to their superiors in Labradorra City, but Bennett immediately regrets this and asks Laura to catch Zero before it's too late.
Lumi and Eve later appear to be okay, since Magnezone's defeat made Lumi's and Eve's consciousness go back to their own body. Eve wanted to one day go back to their bodies but with Zero with them it was difficult. The two of them later goes to Calcenon City, with Lumi breathing in fresh air and Eve informing the player about the other PULSE Machines.
Zero's name is a possible reference to his Umbreon. It could also be a reference that he used to be a regular unimportant grunt, hence a Zero.
Eve's name is a word play on 'evening', a reference to her Espeon.
Lumi's name means 'snow' in Finnish, a reference to her Glaceon.
ZEL's VS sprite is based on that of Grimsley from Generation V of the official Pokémon games.
The types of the three Eeveelutions ZEL uses in battle reflects their personalities-Ice, being rather frail, matches with Lumi, Psychic, relating to the mind, matches with Eve, and Dark matches with Zero's more cruel personality.
The double battle alongside Taka is the only Battle where Zel's team doesn't feature a PULSE. Instead, Taka gets the PULSE.
According to Amethyst, ZEL belongs to Reborn user Ice, and gave permission to Amethyst to use them, as well several other characters belonging to him and another user, Will. The eeveelutions as ZEL's signature pokemons were also part of the original character.