This guide will assume you are familiar with the Heroic version of the fight and expand on how the fight changes in Mythic difficulty. If you are not familiar with this encounter, check out our heroic guide by clicking the button below.
On mythic difficulty, Taloc gains two new abilities: Hardened Arteries and Enlarged Heart. These abilities are active during phases 1 and 3. Both of these abilities are cast at the same time. When Taloc casts these abilities, 10 raid members will be afflicted by Hardened Arteries which gradually slows players until it fully roots them. After being fully rooted, each player explodes dealing damage to all allies within 8 yards. Anyone not afflicted by Hardened Arteries is expected to soak Enlarged Heart. Enlarged Heart will always select a tank as the primary target. Try to take Hardened Arteries to the outside of the room and leave the center of the room as a place to soak the Enlarged Heart.
A few mechanics from heroic are changed in mythic as well. Firstly, Sanguine Static shoots out 5 bolts rather than 3. While on the elevator ride down, there are two Uldir Defense Beams rather than one. The beams can either cross, or be parallel to each other for each set of beams.