Interspace Under Siege is the 15th episode of Bakugan: Mechtanium Surge. It aired on May 29th, 2011.
In the ensuing chaos in Bakugan Interspace, the Brawlers wonder what to do. Rafe makes a note that it is only the Chaos Bakugan that are on a rampage. The Brawlers then summon their Bakugan to save Bakugan Interspace. Meanwhile, Anubias has given Bolcanon to Ben and Krakenoid to Robin. They leave but Anubias stops Noah and gives him Horridian. Once they leave, Sellon reminds Anubias to focus but Anubias mocks her for her failure against Dan. As more and more Chaos Bakugan arrive, Marucho decides to move all of them to Section B and delete the whole area, even though it will create huge damage in the system. Marucho then sends out an Emergency Evacuation but not before Rafe respectively give Marucho Crosstriker for Tristar and give Shun Hammermor for Taylean. Then, they alongside Team Anubias continue to battle the Chaos Bakugan.
Meanwhile, In some type of room, somebody receives a SOS message on his computer, which was sent by Marucho. Back in Interspace, Marucho uses his Bakugan Infinity Tristar. The Brawlers have successfully led all the remaining Bakugan to Area B. Marucho plans to fire up the erase sequence but they notices that Team Anubias are still there. Marucho alerts them and they all run out of Area B but Noah is frozen in fear and can't move which also fuels Mag Mel and Razenoid.
On New Vestroia, Dan and Drago feel a Power Surge and decide to go back to Bakugan Interspace. Just as things look very bad, a streak of lightning and a Dimension Portal appears. Someone appears from this Dimension Portal and it happens to be Spectra Phantom. Paige and Rafe wonder who he is while Marucho reveals that he sent a SOS message to all of the Brawlers' allies and Spectra was the the first one to received it. Then, Spectra sends out Darkus Infinity Helios. Also the Brawlers' were surprise that Helios had an attribute change. Spectra explains that Helios' next evolution required an attribute change. Then, Spectra and Helios decimate a massive amount of Chaos Bakugan but however, he gets hit by some Subterra Iron Dragonoid's. In the smoke, Helios took no damage from the attack because Spectra activated Infinity Helios's new Farbras Ability, (FARBRAS Infinity) and after that Helios beats all of them Anubias get angry. Then with a snap of his finger, Horridian, Bolcanon and Krakenoid jump out from Team Anubias who are in shock and start attacking Infinity Helios. The Brawlers successfully take them down with their brand new BakuNano's that Rafe gave them but Team Sellon's Bakugan come out of nowhere, alongside another bunch of Chaos Bakugan. Then Anubias senses Dan's arrival and he with Drago, arrive back to assist Spectra and the rest of the Brawlers as the chaos continues.
- Titanium Dragonoid
- Infinity Helios
- Iron Dragonoid
- Cyclone Percival
- Flash Ingram
- Infinity Tristar
Mechtogan Titan Seen
- Zenthon Titan (Flashback)
- The Brawlers have the addition of Spectra Phantom to complete their attribute circle. This is similar to what happened in Gundalian Invaders where Darkus was the last attribute to join the Brawlers officially (Ren & Linehalt) and in Bakugan Battle Brawlers where Alice got Alpha Hydranoid from Masquerade.
- This is the first time a Vestal Brawler from the Resistance has had a major role since Bakugan: New Vestroia.
- This is the first time Vertexx and Krowll were seen without Chris and Soon.
- This is the first time that Shun, Marucho and Paige have used their BakuNano.
- Spectra is not included in the MS's Ending Credits at the end of this episode for some reason.
- Marucho says that he send a message to all of their allies, so maybe in one of the episodes we will see old Brawlers from New Vestroia and Gundalian Invaders again.