Note: Run from blue portal to blue portal. There are 8 blue portals. If a portal is surrounded with a red ring and you step inside it then you'll be protected from the Shissar. BUT you have a limited time to stay within any one portal. The game will emote a warning to you when you're running out of time. If you don't get out of the portal in time you'll receive an incurable elemental detrimental that prevents the portals from protecting you. So ensure you run to the next portal with a red glowing effect. If all the portals lose their red glowing effect, you can kite the Shissar around the room until the red glows respawn.
Three more 105 epic x4 Shissar will now come through the chamber portal. Don't panic! They will not hit too hard. You will be told that the magic from the blue glowing portals has now dissipated, so you can no longer use them for healing. However, you will get a temporary hotbar with abilities that allow you do deal damage, heal yourself and close the chamber portal. Ensure you take time to read what the new abilities do. Run to the exit portal at the back of the room if you need time to regroup, and then zone back in. If you're smart you will fight the Shissar one at a time, so just be mindful of your AOE. You can target the portal by using your tab button. You may kill the 3 Shissar x4 mobs first and then close the portal or close the portal and then kill the shissar
Note: Tip for 3 Shissar. Pull them down to room below. Fight them there by running around edge of room and casting all the spells as soon as they come up. This will keep you far enough away from the mobs so you don't get One Shotted.
Note: Optional Way: Move to the back of the room (other side of where the ramp leads up) start with killing the portal (use "collapse portal" ability first then it's a rather easy kill it; can be ranged) then kill the mob in the center then one on the left (left of the ramp that leads up) then the one on the last one, the mobs seems to hit harder as long as the portal is up