-  Shards of Light
They can call a Summoned Elhudan upon them. When the summoned add dies, the Flickering Elhudan heals to full health. This will happen if you kill the add, but even if you leave the add alone, it will automatically expire after a few seconds (not sure exact timing). Essentially, if it summons the add, you have a few seconds to finish it off before it heals.