The Magajinder is a plastic model robot (Plamo) which is manufactured by (or for) the Evil Deity Organization.
The Magajinder made its debut in the manga series for Crash B-Daman, specifically in the chapter Infiltration!! Into the Assassin Organization Magajin which is also the debut chapter of Kyousuke Arasaki. Therein, Kyousuke is seen assembling a Magajinder plastic model robot but was interrupted by an infuriated Kodoh Kuraki.
The Magajinder is a toy which was associated with Kyousuke's calmer persona and his harmless hobby of meticulously building robots. However if one would disturb Kyousuke's peaceful plamo building session, it will cause him to snap.
The Magajinder made an appearance outside of Crash B-Daman such as in Tomoya Kuratani's in-blog four panel comic (yonkoma) for his other manga series DFK (Devil Football Kingdom).