Big Core MK I (ビッグコア) is a recurring boss in the Gradius series.
Big Core MK I is the famous staple boss in the Gradius series. They are usually found in a Gradius game in one form or another as an actual stage boss, in a boss run, or as regular enemies. (In Gradius V, they are very numerous in stage 3 at several parts and in stage 7 at the beginning of the stage.) In Gradius Gaiden, it is in the second stage as one of the boss debris. In Nemesis 2 (MSX) before boss 4, a fleet of them appear for you to destroy.
Other games have made several variants of the Big Core MK I that have it with extra armaments, different attack patterns, or transformations.
In Gradius NEO Imperial, Big Core MK I is the player's vessel instead of the Vic Viper. Here some additional weapons are available besides the traditional four laser shot.
Big Core MK I attacks by shooting four blue lasers at the player while moving up and down. They have only one core (the weakness for most bosses) which is protected by four panels. It is usually easy to destroy.
However in Jikkyou Oshaberi Parodius, it becomes a little harder to deal with. At first it will attack normally, but it will suddenly turn around and begin attacking you from behind. When it returns to the right side, it will move faster and shoot it's lasers haphazardly and non-sequentially.
The Big Core appears in the second episode of the Salamander anime series. It emerges from the Bacterian infested planet the heroes investigate, sending a huge wave of Rugals when they retreat. It reappears again later, as the Gradian forces shoot it down and apparently destroy it.
Big Core, as it appears in Gradius.
Big Core, as it appears in the X68000 port of Gradius.
Big Core, as it appears in the NES port of Gradius.
Big Core, as it appears in the ZX Spectrum version of Nemesis.
Big Core, as it appears in Salamander. It is fought 3 times.
Big Core, as it appears during the Boss Rush Stage in Gradius II. Image from NES port.
Big Core, as it appears during the Boss Rush Stage in Nemesis 3.
It also guest stars in a mini game in Blades of Steel.
In Otomedius Excellent, if Tita Nium is used by the player, then she comments that Old Big Core's code is incompatible (to her BC-SYSTEM, it would seem) when she enters the barrier section of the ship to fight the gunwall.
The background video for GRADIUS 2012 in beatmania IIDX 20 tricoro sees the Vic Viper joined by a friendly Big Core MK I.