Perma

Perma, short for "permanent Shadow Form", is an old term used to refer to any build with maintainable Shadow Form. Those builds are so ubiquitous (used in almost every SC) that the word "perma" has become redundant.

Common Skills

Shroud of Distress

Almost every perma build uses Shroud. It perfectly complements SF: one neutralizes most spells, while the other blocks most attacks. In many situations, permas like to let their health drop below 50%, usually so they have a chance to block interrupts.

shadow steps

Death's Charge is a staple for most perma builds. Dark Prison can be added to essentially have an extra copy of DC, but more expensive and without the healing.

Heart of Shadow is useful for jumping forward when the only suitable target is behind you. Viper's Defense is a useful alternative, with slightly shorter cooldown and AoE poison. If you target yourself with HoS or Viper's, you will jump in a random direction but more than twice as far - this can be useful if you are bodyblocked against a wall.

perma Dash

Dwarven Stability and/or Dash are often used for permanent anti-KD and speed boost. This combo is a key part of "dasher" and "gater" builds, but is also used in other builds.

Sliver Armor/Whirling Defense

A "terra" build is one with either Sliver or Whirling, using plenty of ranged aggro to solo enemies.

"I Am Unstoppable!"

IAU is mostly used for anti-KD, but is also useful for removing cripple and providing an armor buff that bypasses the +25 armor level cap.

no BU

Without an Essence of Celerity, an extra skill is needed to maintain SF. Deadly Paradox is the default option, as it doesn't require a secondary profession. Other options include Glyph of Swiftness, Arcane Echo, Serpent's Quickness, and Quickening Zephyr.

Damage Reduction

As well as the spell immunity, Shadow Form reduces incoming damage by 5 for each assassin enchantment on you. However, this damage reduction is bugged:

If you re-cast an enchantment before it expires, it counts as 2 enchantments until the first one would have expired. Long duration enchantments with relatively short cooldowns, such as Way of Perfection and Way of the Master, can effectively be used to stack a lot of damage reduction.