You can find the Maw of Souls dungeon entrance within Stormheim, The Broken Isles.
The coordinates are (52.5,45.5)
1. Ymiron, the Fallen King
/i Tank use active mitigation for Dark Slash. Move away from boss for Screams of the Dead (fears everyone within purple circle). Careful of knock back Winds of Northrend, dont have your back to any purple ghosts.
Heroic/Mythic Differences: Any remaining Essences of Bane (purple ghosts) will turn into Risen Warriors, focus kill them. Soak some Banes to stop too many warriors spawning, careful how many soak because deals high damage.
/i Cosmic Scythe focuses a random player, dodge the line of weapons. Fragment stuns a player & spawns 2 adds, focus kill these soul adds. Kill Servitor adds that spawn, interrupt Void Snap.
Heroic/Mythic Differences: Boss casts Nether Rip under players, move away from these purple patches.
This fight has 2 phases. Phase 1: Tenticles. Phase 2: Push back, front of ship is broken & then boss is attackable.
/i Focus kill Destructor Tentacles, then Grasping Tentacles. Stay away from holes in floor. Healer dispel Taint of the Sea dot. Interrupt Torrent. Aims frontal cone Corrupted Bellow in direction she facing, move opposite side. Avoid blue swirls on floor.
Heroic/Mythic Differences: Taint of the Sea dot will leave green swirl & deals damage to whole party, healer dispel this when your group has high enough health to take the damage.
Brackwater Barrage is a green frontal cone aimed at the sides of the ship, to avoid this run to the opposite side her casting hand is facing towards.