A monster from the game Minecraft.
Amongst the Japanese community it has earned the nickname "匠" or "たくみ (Takumi)", which translates to "Craftsman."
It is known as one of the most dangerous mobs in the game. Like most Minecraft mobs, it only spawns in the dark or at night, but it's completely unharmed by sunlight, allowing it to still be found during the day. Its only attack is to explode, destroying itself, the player, and whatever blocks are nearby. This, combined with its silent nature--only making its trademark "Tsss" (or "シュー" as it's known in Japanese) when it's about to explode--has given it a notorious reputation for taking players completely by surprise.
Being one of the most memorable and original mobs in the game, it has become a kind of mascot for Minecraft.