Successfully complete the game and get the third ending to get the Ardebaran Mask. To get the third ending, let at least one person escape in Chapter 17, and let Keith live Chapter 24 (slightly damage him). The Ardebaran Mask does a lot of damage, and it makes the victim walk straight.
Evil Kick
Successfully complete the game and get the fourth ending to get the Evil Kick. To get the fourth ending, kill everyone in Chapter 17, and let at least one person escape in Chapter 21. The Evil Kick is a very powerful trap that sends a victim flying across the room.
Evil Upper and Evil Stomp
Successfully complete the game and get the first ending to get the Evil Upper and Evil Stomp. To get the first ending, kill everyone in Chapter 17 and Chapter 21 (Two Wrongs Equal One Right).
Extra Ark
Enter "Astarte" as a name for an extra 2800 Ark.
Magic Sac
Successfully complete the game and get the second ending to get the Magic Sac. To get the second ending, let at least one person escape in Chapter 17, and kill Keith in Chapter 24 (Shared Wounds). The Magic Sac does not do any damage, but it immobilizes an enemy, allowing you to push them anywhere.
Sound Test
To gain access the sound test you must first go to the title screen, then press R1, R1, R1, R1, R2, R2, R2, R2, R2, R2. Once you've entered the code you should hear a sound that will notify that you've done the code correctly. Then on the Mode Select screen an option called Sound Test will then be accessable.
Suezo
Get all four endings and save them to a memory card to get the one-eyed yellow monster from Monster Rancher, Suezo. The Suezo has no animation, but is a very powerful trap.
Ardebaran Mask ...