If players manage to get Pure Black Character Tendency and Mephistopheles spawns in the Nexus. Players are more likely to kill Ostrava in 1-2 because of the need to kill the Phalanx boss and level up. During 1-2 Ostrava will increase slightly in health and damage and during 1-3, 1-4 Ostrava will have become stronger than he did in 1-1 and may even fight back if prompted. Players can easily backstab him repeatedly without much retaliation or finish him off after he has killed an enemy by himself. If Ostrava is encountered in 1-1 or 1-2 he won't be much of a fight, it is easy to utilize nearby enemies like Blue-Eye Knights to kill him single-handedly or even letting him kill groups of dreglings. He then dies from his wounds, or possibly kills himself, before he reappears at the end of the hall, as a Black Phantom. He will tell the player to seek out Old King Doran and gives the player the Mausoleum Key. He is finally encountered in 1-4 in the hall just after the Blue Dragon. He can be found in 1-3, being attacked by Red Eye Knights. He can be talked to through the portcullis in the very first room of the area, where he will request the player's help. After being rescued, he will give the player 3 Dark Moon Grass as thanks and will then patrol the area.
Here he will be cornered by some Dreglings and Boletarian Soldiers. He will move to 1-2 after the defeat of the Phalanx. After talking to him, he will start to patrol the surrounding area and kill the enemies. Talking to him now will net the player the Brass Telescope. Upon doing so he will drop down and stand where they once were.
When talked to, he will ask the player to kill them. Ostrava is first found in 1-1 on a platform above some Dreglings.