Curg's Cthulhu Guide: Joust

Sanity Break: Cthulhu sends out a terrifying blast of energy, dealing damage to all enemies hit and reducing their Attack Speed. Enemies hit by this ability also do reduced damage to Cthulhu for 6s.
This ability applies 1 stack of Torment, 2 if the enemy hit is facing Cthulhu or Fears them instead if they are afflicted with Insanity. Successfully consuming Insanity permanently increases the base mitigation of this ability.

Ability Type: Cone, Fear, Damage
Damage: 100 / 150 / 200 / 250 / 300 (+40% of your Magical Power)
Attack Speed Slow: 20 / 22.5 / 25 / 27.5 / 30% for 3s
Fear Duration: 1.5s
Damage Mitigation: 20% + 0.5% (Max 30%)
Cost: 60
Cooldown: 10s

Sever (Ultimate Form): Cthulhu swipes down at the ground beneath him, creating 3 large projectiles. These projectiles damage enemies and apply a stacking Protection Reduction debuff. This ability does not proc item effects.

Ability Type: Line, Debuff, Damage
Damage: 100 / 140 / 180 / 220 / 260 (+25% of your Magical Power)
Protection Reduction: 4% stacking up to 4 times
Debuff Duration: 5s
Cost: 0
Cooldown: 1s

The Mire: Cthulhu summons a portal creating a slowing field of eldritch mire at the target location. The Mire continues to grow as the portal fires out two masses of corruption that hit and damage all enemies in the field. The first shot also Slows enemies while the second Roots them, both hits applying 1 stack of Torment.

Ability Type: Circle, Crowd Control, Damage
Damage per shot: 60 / 105 / 150 / 195 / 240 (+30% of your Magical Power)
Slow: 10%
Corruption Slow: 35%
Corruption Slow/Root Duration: 1s
Mire Duration: 3s after ability end
Cost: 50 / 55 / 60 / 65 / 70
Cooldown: 14s

Devastate (Ultimate Form): Cthulhu fires a devastating blast of psychic energy that damages and knocks up enemies.

Ability Type: Circle, Knockup, Damage
Damage: 140 / 175 / 210 / 245 / 280 (+20% of your Magical Power)
Cost: 60 / 65 / 70 / 75 / 80
Cooldown: 5s

Rushing Terror: Cthulhu creates two twisting projectiles at his sides as he unfurls his wings and charges forwards, damaging, stunning and knocking away enemies hit. The projectiles follow at a slightly slower pace but travel further, damaging enemies as well. Enemies hit by Cthulhu or the projectiles gain 1 stack of Torment.

Ability Type: Dash, Knockback, Damage
Damage: 70 / 110 / 150 / 190 / 230 (+30% of your Magical Power)
Stun Duration: 0.4s
Projectile Damage: 40 / 70 / 100 / 130 / 160 (+20% of your Magical Power)
Cost: 60 / 65 / 70 / 75 / 80
Cooldown: 16s

Transfuse (Ultimate Form): Cthulhu transfuses his own life force into the area around him giving Allies Health, Movement Speed and Power. Enemies are also hit, taking more damage the closer they are to Cthulhu. This ability damages Cthulhu for 4% of his Maximum Health. If Cthulhu is below 20% Health, this ability does not damage Cthulhu but all Ally effects are reduced by 50%.

Ability Type: Circle, Heal, Damage
Damage: 120 / 140 / 160 / 180 / 200 (+20% of your Magical Power)
Ally Healing: 5 / 6 / 7 / 8 / 9% Max Health
Power: 20 / 25 / 30 / 35 / 40
Movement Speed: 20%
Duration: 3s
Cost: 70
Cooldown: 6s

Cthulhu reveals his true form as he plunges the battlefield into R’lyeh while any enemies caught nearby are damaged.

In this form Cthulhu gains increased Health, becomes immune to Crowd Control and gains access to new abilities. Enemies near Cthulhu gain stacks of Torment, increasing in pace if they are facing him. Enemies also suffer the debuff effects of Sanity Break, causing them to deal less damage to Cthulhu.

Ability Type: Circle, Buff, Damage
Damage: 160 / 205 / 250 / 295 / 340 (+50% of your Magical Power)
Max Health: 25%
Duration: 10 / 11 / 12 / 13 / 14s
Debuff Radius: 50
Cost: 100
Cooldown: 120s

*NOTE* Cthulhu cannot use relics while in his ultimate form.