<p>Generally speaking, not killing a boss does not affect its <a rel="nofollow" href="https://tibia.fandom.com/wiki/TibiaWiki:Bosses_Spawn_Frequency">chance of spawning</a> again. So if a boss' spawning interval is between 7 and 15 days, not killing it won't make it reappear faster. Bosses which can spawn on 2 or more days in a row are due to other mechanics:</p><ul><li>Gaz'haragoth, like you mentioned, spawns every day on the Roshamuul Mountain as part of the Roshamuul Quest world progress.</li><li>Bosses with multiple spawn locations, such as White Pale or Tyrn, can spawn two days in a row because each day will be a spawn on one of the locations. Each location's interval is independent from the other.</li><li>Bosses that spawn due to Mini World Changes, for example Bank Robbery Bosses. MWCs have a chance to be triggered every day and there's a small chance it will happen two days in a row.</li><li>Bosses that can be forced to spawn due to the <a rel="nofollow" href="https://tibia.fandom.com/wiki/Varying_Monster_Spawn">Varying Monster Spawn</a> system, for example Crustacea Gigantica (not really a boss but usually deemed so by players) or Burster.</li><li>Event bosses like The Mutated Pumpkin that spawn daily during the event.</li></ul>