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Last updated for version 1.2.3
The Solipsist class is defined by its unique Solipsism ability that allows it to divert both damage and healing to their Psi resource. All Solipsists start with the Solipsism ability and it cannot be unlearned.
Psi can be increased by level, willpower, items, and by learning additional talents in the Solipsism tree. A large Psi reservoir allows Solipsists to survive with low constitution and health, so the class can work well with otherwise low health races such as Yeeks.
Solipsists can be built in many different ways due to the wide variety of talents available to it. It has strong direct damage mind powers that can obliterate enemies at range. There are thought-form pets that can be possessed for scouting or to engage otherwise dangerous opponents while the Solipsist sits back in safety. Three talent trees in sleep related abilities provide a host of crowd control options. The multitude of healing and damage mitigating talents can also turn the Solipsists into a very resilient tank, especially in combination with antimagic and fungal abilities. The class even has two melee oriented talent trees that can make it a dangerous fighter in close quarters.
One important thing to remember is that if a Solipsist runs low on Psi, they gain the Solipsism debuff, which reduces their global speed dramatically and usually results in a very quick death. Keeping enough Psi—which is also health—in stock is thus vital to the survival of the class.
There are two major routes for "spellcaster" Solipsists: Distortion effects, which amplify each other, and straight up Psi effects.
All Distortion talents cause a debuff called Distortion on the target, and if this debuff is active when another Distortion talent lands, that talent's effects will be supercharged. The Distortion Bolt ability, for example, is a standard bolt spell, unless it strikes something that is already distorted, then it turns into an area of effect nuke with much higher damage.
The Psychic Assault tree revolves around doing mind damage, as well as confusing, debuffing, and brainlocking the target. All the standard stuff is there: a beam, a PBAoE ring, a targeted confusion, and a targeted damage and debuff.
The Dream Smith and the unlockable Dream Forge talent trees allow for melee combat. Although Solipsists do not start with the Mindstar Mastery tree, they can still purchase it from Zigur for gold. All Dream Smith abilities are synergistic with each other, making each other stronger. Taking the entire tree gives you a weapon with uncanny accuracy, mind and fire damage, as well as giving you the ability to melee "attack" in a bolt as well as stun with your melee attacks and hit in an AOE.
No less than three of the Solipsist trees involve sleep effects: Slumber, Nightmare, and Dreaming. Each has a different form of sleep ability with differing strengths and weaknesses. Nightmare, for example, is a cone AOE which also does nightmare damage, but breaks extremely easy. Slumber is a single target sleep ability, which is very hard to break. Sleep is an AOE that, at higher levels, spreads like a contagious disease.
Each tree has support abilities based around sleeping targets:
The Dreaming tree has a powerful self buff, as well as a targeted phase door like teleport, and an ability that locks down all sleep effects at the cost of a constant Psi drain.
The Slumber tree can cause all sleeping targets to take mind damage upon waking, as well as granting a passive buff that makes it harder to wake up (and easier to fall back asleep) from your sleep abilities. The final ability, Dreamscape, allows a Solipsist to invade a sleeping target's dreams and utterly crush them.
The Nightmare tree has a summon spell, Inner Demons, which has a low chance of summoning a demon to attack a target. This chance is doubled if the target is asleep. Waking Nightmare is a damage over time spell with a similar chance of causing status ailments, which again is doubled on sleeping targets. Finally, Night Terror vastly increases your damage on sleeping targets, and also summons a powerful creature if you manage to slay a sleeping target.
The sleep effect can be countered by confusion resistance, so it is important to have some backup talents to deal with enemies that have high confusion resistance or even complete immunity.