<p>Not all but Yes, they can appear immediately after saving the server. I check this way often and I have met some bosses many times. There are even statistics on tibiabosses at what times they can appear.appear.</p><p></p><p>For sure <strong>Groam <img alt="" src="https://vignette.wikia.nocookie.net/tibia/images/e/e0/Groam.gif/revision/latest?cb=20171218214539&path-prefix=en" style="height:64px; width:64px"></strong>, <strong>Midnight Panther<img alt="" src="https://vignette.wikia.nocookie.net/tibia/images/1/15/Midnight_Panther.gif/revision/latest?cb=20140123150714&path-prefix=en" style="height:64px; width:64px"></strong>, <strong>Zevelon Duskbringer<img alt="" src="https://vignette.wikia.nocookie.net/tibia/images/1/15/Zevelon_Duskbringer.gif/revision/latest?cb=20080711144417&path-prefix=en" style="height:64px; width:64px"></strong>, (and rest Vampires) <strong>Dire Pinguin<img alt="" src="https://vignette.wikia.nocookie.net/tibia/images/d/d5/Dire_Penguin.gif/revision/latest?cb=20070619120750&path-prefix=en" style="height:32px; width:32px"></strong> I met these bosses right after ss.</p><p>I think that most bosses can be found after ss. Despite the fact that spawn is random.</p>