Increase the range of Restore Soul by 300% and reduce the time between Healing ticks by 20%.
Heal for 70-350 every 1s while channeling Restore Soul.
Increase the range from the main target at which Restore Soul's secondary Healing can target allies by 6-30%.
Reduce the cast time of Shadow Travel by 10-50%.
Fade to Black
Reduce the Cooldown of Shadow Travel by 0.8-4s after activating Restore Soul. This can only occur once every 5s.
Increase your Movement Speed by 8-40% while Shadow Travel is active.
Seris is one of the easiest supporters in the game. "Blood pact IV" I have at level 4, so that you have while you heal others also a possibility of self-preservation. I also have "Soul Forge IV" at level 4 so that you can heal as many allies as possible. "Fade to Black III" and "Veil III" I have on level 3 so that you can escape in dicey situations. If you are not so skilled with Seris you can increase Veil and decrease Fade to Black. At the last place you can take different cards you want examples would be "Dark Whisper", "revenant" or "sorceress".
At the beginning of the game it is best to take the items chronos and nimble. After that you can get haven or veteran. And additionally then kill to heal, because you also get the healing when a healed player eleminates someone and it is not influenced by cauterize.