Shaman is an expert of black magic, specializing in DOT, AOE damage and debuffs.
Passive: Bloody Aura
When Shaman takes damage, red aura surrounds him. The more hits/damage he takes, the more strength aura gains , increasing intensity and expanding. Aura and it's strength affects Shamans attacks and it starts to disappear when out of battle for too long (like over 10 secs).
Primary Attack: Pain
Shaman focuses his magic on enemy to cause damaging implosion (think of Anima from FFX). Damaged enemy gets stunned for 1 second. When aura is active, surrounding enemies will share it's pain, taking damage, which amount and range depends on aura strength.
Use: Target an enemy and hold LMB to charge attack. It needs to be charged fully, which takes 1 sec or so, and damage is inflicted directly to enemy. Time you need to charge attack depends on your attack speed and it depends on stability if the charging can be cancelled.
Secondary Attack: Poisonous Dash
Shaman does a backdash, leaving a poisonous shroud behind. The shroud lasts for few seconds and poisons enemies in it's area. Poison lasts for few seconds (renewing when in shroud) and poisoned enemies take damage over time and deal 15% less damage.
When aura's strength is over half of it's capacity, Shaman leaves also a decoy. Enemies attacking decoy take backfire, restoring also very slight amount of health to Shaman.
First Skill: Rain Dance
Shaman creates a cloud over him that rain acid. Enemies in range of rain take damage (rate damage depends on aura) and are inflicted defense melting, which makes them take 15% more damage from attacks (excluding rain).
Ultimate Skill: Calamity
Shaman discharges all his aura to summon a herd of deadly maggots. Maggots have a limited lifetime and are immune to damage. Their number and lifetime depends on strength of discharged aura, but their lifetime is also randomized slightly, so they don't disappear all at once. Enemies attacked by maggots will aggro to them. When maggot dies, it leaves behind a poisonous shroud similar to secondary attack, but it lasts much shorter and has weaker poison.
I intentionally didn't give any numbers (except debuff %), including cooldown and energy costs, because it's all subject to balance anyway and I'm no good in that stuff.