Called "King of Bats", Antasma makes for his namesake with a mask that mimics bat ears, long pointy fangs and a cape that mimics a bat's wings. Mostly cloaked, Antasma has sharp claws in his hands and a skeletal body.
In his first appearance, his head has many thorns in both sides, his neck is adorned with a bat-shaped bowtie with a spiral knot and a long red tie. Underneath, instead of legs, Antasma floats with a wispy ghostly tail.
When not in these forms, Antasma is a menacing purple cloud of darkness with only his eyes visible or a small bat that looks pretty much like his disembodied head with bat wings.
Long ago, Antasma was an ordinary bat that sought power of the Dark Stone. Antasma managed to get the Dark Stone but knowing that he was going to use it for the evil intentions, the Pi'illo's banished him into the dream world. Just before he was banished, Antasma destroyed the Dark Stone and pieces of it landed on the Pi'illo folk and turned them into stone. Antasma then waited for years where he has the chance to return to the real world. During the beginning, Antasma fights Mario in a tutorial battle. Mario manages to win but the blimp crashes onto Pi'illo Island. However, this turns out to be all a dream by Luigi. During the battle, Antasma is referred to as "????" due to his true identity being secret.
Antasma first officially appears where he has taken Princess Peach into the dream world. Mario has no choice but to follow him and Antasma is eventually cornered by Mario and Dreamy Luigi. Antasma then creates a clone of Mario and assists the clone in battle. However, Mario was able to defeat this doppelganger but Antasma ends up escaping into the Dream's Deep. Antasma is eventually cornered by Mario, Dreamy Luigi, and Prince Dreambert but suddenly, Bowser appears. Antasma, delighted to see such power, convinces Bowser to aid him in the fight with Mario, Dreamy Luigi, and Prince Dreambert. Bowser eventually agrees and they all get into a fight. Mario's team seems to have the upper hand, but Antasma manages to power up Bowser even more and he knocks out everyone with his fire breath. Antasma then promises that Bowser will get power after getting the Dream Stone and Bowser gracefully accepts. Antasma then escapes from the dream world with Bowser where they head to Dozing Sands to get the Dream Stone.
At Dozing Sands, Mario, Luigi, Prince Dreambert, and Starlow are all too late as Antasma and Bowser have acquired the Dream Stone. Antasma gloats on his success to Prince Dreambert, saying they will now awaken the Dream Stone at another location. This location is later revealed to be Mount Pajamaja, where Antasma and Bowser have positioned themselves at the summit. Mario and the rest managed to catch up but Antasma then takes out a boom box and starts playing strange music that makes Mario and Luigi sleepy. Prince Dreambert quickly identifies them as Dreambeats, and Antasma gloats saying how the Dreambeats will put everyone in the area to sleep. Prince Dreambert and Starlow aren't affected, but Mario and Luigi are falling asleep and Dreambert admits that he cannot defeat Bowser without Mario and Luigi (Bowser has his ears covered at the time so he isn't affected by the Dreambeats). Everyone else escapes and Antasma decides to use some of the Dream Stone's power. Antasma then decides they need a new castle and uses the Dream Stome to help create it. Bowser dubs it "Neo Bowser Castle" and he and Antasma plan their next move and surrounds the castle with a barrier.
This move was revealed to be the capturing of Princess Peach. Bowser sets Mario and the rest up while he and Antasma have her in their clutches. Although Antasma and Bowser aren't seen for a while, they know of Mario and the rest's plan to awaken The Zeekeeper by assembling the pieces of the Ultibed and even has thieves steal one of them. Once the barrier has been shattered by The Zeekeeper, Antasma and Bowser set up their next plan to impede Mario and the rest's process. This plan involved using Kamek to mess up the paths and Antasma opens a portal to the dream world which Kamek escapes to. The plan was used three times until Kamek was finally defeated. Antasma then hatches up another plan by turning himself into a pillow and using Bowser's energy to help power the castle. This plan was eventually foiled as well and Antasma and Bowser have no choice but to fight Mario and the rest. However, Bowser betrays Antasma, saying that only he could rule the world and takes off with Peach and the Dream Stone. Antasma is upset and gets into a brief brawl with Prince Dreambert before entering into the dream world. Dreambert follows Antasma into his artifcial dream and comes out, defeated, soon after. Mario follows behind and instantly fights Antasma. After a long battle, Antasma eventually explodes, never to be seen again.
Antasma is fought three times. His first battle takes place on route to Pi'illo Island. The second time Mario faces him is when he faces Bowser for the first time. Antasma is fought for the last time in his artificial dream.
In his last battle, Antamsa mainly uses the Antasmunchie orbs that surround him to power himself up before using these other attacks. Antasma can eat up to 3 Antasmunchies each turn, and only does so at the start of his turn.
- Bat Swarm: Antasma turns himself into many bats that will swarm in Mario's direction (may cause tripping). Mario can use his Hammer in the first Bowser battle, since the bats will attack their target once every 1 or 2 seconds, but Bowser will replenish his health if Mario gets hit. When Antasma is being fought on his own, Mario can jump on the bats if said bats are at ground level. Destroying the bats will damage Antasma himself. This is Antasma's only attack in his first battle.
- Clone Energy Blast: Antamsa clones himself and one of the duplicates will charge up the energy blast and sends it at Mario. Mario has to use his hammer to knock the ball at the real deal.
- Nightmare: After Antasma gets a certain hit in on Mario, Mario will lose his consciousness and Antasma will charge at Mario firing energy blasts at him. Mario can jump the blasts but has to find his way out, and there are dark portals everywhere. Only one is the real escape route. If Mario falls down a wrong portal, he will have to endure a dimension full of chainsaws (though you can change the gravity by tilting the 3DS to avoid damage since the chainsaws do not change their position and there are gaps between them), so he must not lose his way. If Mario goes down the right one, there will be plenty of Coins and Mushrooms to greet him. Outside the nightmare, Mario will wake up and becomes shocked. Escape costs an extra turn in the Battle Ring.
- Dreamy Luigi Steal: Antasma will snatch Dreamy Luigi and hide him in one of the Antasmunchie orbs. He will then shuffle the orbs around and if Mario doesn't free Dreamy Luigi, Antasma will eat Dreamy Luigi and power up even more. However, Antasma will spit Dreamy Luigi out and the latter will fuse back into Mario. The initial attack deals no damage but cannot be avoided.
- Rest/Antasmunchie Attack: Antasma will hang upside down and encase himself in a barrier and his Antasmunchies will then start to attack. In their attack form, the Antasmunchies cannot be stomped and can charge from all sides. Mario must use his hammer to repel them. Antasma will sometimes turn the screen upside down, forcing Mario to face the opposite way to destroy the Antasmunchies. Also, every turn Antasma is resting, he will recover 200 HP.
- Dark Orb Blast: Antasma's strongest attack. Antasma will then start to hover a bunch of orbs around in the air and will try to hit Mario with them. Mario must get into the center of this and jump over the attack or Antasma will unleash a shockwave that does over 100 damage. If Mario dodges this attack, Antasma will get damaged instead. Antasma always does this attack 3 times in a row before stopping (four if he ate 3 Antasmunchies).
The Nightmare Attack can be avoided all together if Mario dodges every one of Antasma's attacks. Using Luiginary Wall and Luiginary Typhoon works wonders in this fight as it can damage Antasma and the Antasmunchine orbs. It should also be noted that Prince Dreambert will always heal Mario by 30 HP at the end of each turn.
Main article: Antasma X
Antasma X is the upgraded version to Antasma, who appears as the second-to-last X boss in the Battle Ring. His appearance is that his cloak and skin went from purple to blue, and has light blue eyes. His stats have also been advanced, given higher HP, POW, DEF, etc.
- "Antasma" can be actually the Portuguese word for "Ghost", which is "Fantasma" but cutting off the "F".
- The F being cut off may also be a pun on the prefix "anti-" (against).
- Antasma is very similar to Cackletta from another Mario & Luigi game Mario & Luigi: Superstar Saga.
- They both wear long capes.
- They both are based of vampires.
- They both can transform into multiple bats as one of their attacks.
- They both take over Bowser's body at some point in the game.
- They both are similar in height (though Antasma does appear taller in his true form).
- It should be well noticed that a glitch tends to happen right after the second fight with Antasma. It usually involves the present not opening and Mario is still doing his battle pose with Prince Dreambert still smiling. This glitch is usually fixed by not using any Luiginary Attacks during the battle.
- This is the only battle in the dream world where Mario fights alone without Dreamy Luigi fused into him (only after Antasma has snatched him away).
- Antasma is one of few characters in the Mario & Luigi series that has eaten one of the main characters in this game. In this game, Antasma is able to eat Dreamy Luigi during the second battle.
- In Mario & Luigi: Superstar Saga, Bowletta is the one that eats Mario and Luigi (during her second phase).
- In Mario & Luigi: Partners in Time, Yoob is the one that eats Mario, Luigi, Baby Mario, and Baby Luigi. Also, Petey Piranha also eats Princess Peach at one point in the game.
- In Mario & Luigi: Bowser's Inside Story, an out-of-control Bowser inhales almost everyone that was present in Princess Peach's Castle at the time. Also, a Sculet eats Starlow at one point in the game.
- In Mario & Luigi: Paper Jam, Petey Piraha is able to eat either Mario, Luigi, or Paper Mario if he manages to grab one of them.
- Antasma speaks in a similar broken English with Mario & Luigi: Superstar Saga's Hermie III as they say the letter v instead of w, and replaces the ve sound with 2 f's.
- The fact that Bowser would betray Antasma is a surprise, with no clues, similar to how Sir Miles Axlerod was the main antagonist of Cars 2 and did not give any hints as to this.