While traverse through the dungeon, Mari appears and blows one of these up, then using a crouch animation to pick up its organs.
One Quest says that DK Mark-IIs were dispatched by Lord Perseo, suggesting that the Mark-Is (and possibility Mark-III) were created and produced by the god.
The DK Mark-I is capable of a few attacks. One is where it shoots out three glowing spheres in front of it at 3 different angles, one in front, and two 45 degrees above and below that. Another is where it will shoot out a single, slower moving orb that will chase after a player. Slower moving characters usually have a hard time outrunning it, and will usually get hit, even with the use of a skill. A third is where it will thrust its arm out and create an electrified area around one of the players.
The DK Mark-I is also capable of summoning a Hideous Borer, though it is possible to interrupt the summon.
Prior to defeat, the DK Mark-I will explode, dealing damage to anyone nearby.