Power Design (4e Guideline)
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 General advice
 Power Source
There's little justification for creating a new power source, since almost everything falls under the existing sources. Arcane covers anything to do with the Elemental Chaos (i.e. demons, the elements), Dragons and most things vaguely magic-like. Divine covers the Astral Plane (devils, most deities). Primal is "the spiritual expression of the world itself". Shadow includes undead things, the Shadowfell. From Heroes of Shadow: "Divine power requires, at least initially, devotion to an external source. Arcane magic can entail study and hard work. Martial excellence comes through difflcult training and mastery of refined techniques. Psionic power hones the mind in a similar way. Shadow magic, unlike all of the foregoing, requires simple surrender."
If you do make up your own power source, you need to consider that this cuts your class off from many feats and options that have a power source prerequisite.
- Arcane - Spells
- Divine - Prayers
- Martial - Exploits
- Primal - Evocations
- Psionic - Disciplines
Familiarize yourself with PHB, p. 55. Your power should have the following keywords:
- Your power source: Martial, Arcane, Divine, Primal, Shadow or Psionic
- Attacks need the Weapon or Implement keyword. Most racial attack powers are an exception, see the Racial Powers guidelines.
- If an attack power causes typed damage, the power gets that keyword.
 General keywords
- Charm - Mental effects that control or influence the subject's actions.
- Conjuration - Powers that create objects or creatures of magical energy. Do not confuse with Summonings.
- Fear - Effects that inspire fright.
- Healing - Powers that restore hit points.
- Illusion - Powers that deceive the senses or the mind.
- Poison - Substances that hamper or impede a creature.
- Polymorph - Effects that alter a creature's physical form.
- Reliable - If you don’t hit when using a reliable power, you don't expend the use of that power. In practice, this is only used with Martial daily powers.
- Sleep - Powers that cause sleep or unconsciousness. Be careful with this, see below.
- Stance - A stance power lasts until the end of the encounter, for 5 minutes, or until you use another stance power.
- Teleportation - Powers that transport creatures instantaneously from one location to another.
- Zone - Powers that create lingering effects that extend over an area.
 Class specific keywords
- Augment is used by Psionic classes.
- Beast (Martial Power, p. 42) is used with classes that have a Beast companion.
- Beast Form (Player's Handbook 2, p. 84) is used with the druid Wild Shape class feature.
- Invigorating (Martial Power, p. 7) is used with Martial attack powers only.
- Rattling (Martial Power, p. 7) is used with Martial attack powers only.
- Full Discipline is used by Psionic classes.
- Summoning is used for Wizard summon spells (see Arcane Power).
If you want your powers to use a keyword used by a specific class, your class is probably a "type of" that class. For example, Mages are a "type of" Wizard, so inherit everything that has Wizard as a prerequisite.
Some conditions are more powerful than others.
- Stunned and restrained conditions should not be introduced until paragon tier.
- Restrained and unconscious should be considered carefully before being used in a power.
- Dominated and petrified should be restricted for use by monsters.
- At-will powers and Encounter powers should not have effects that last beyond the end of the player's next turn.
- Daily powers may have indefinite durations. This might include:
- Ongoing damage, or a condition that ends on a saving throw.
- A stance
- A zone, conjuration, mode of movement or some other effect that can be sustained, or that lasts until the end of the encounter.
 Misses and Effects
- All utility powers have an Effect that describes what the power does.
- For attack powers, Effects occur wherever or not the attack hits, after the attack is resolved. Its use in at-will and encounter powers is limited in scope - often used for maneuvering ("Switch places with a willing adjacent ally"), to lay down a temporary zone, or to grant a minor benefit to the character or an ally.
- Misses are almost exclusively used with daily attack powers. This is usually some lesser form of the hit result: hit damage is halved; "save ends" conditions just last until the end of your next turn, and so on. A power would not have both an Effect and Miss. Rarely, an at-will might have a Miss, for example the Fighter's Reaping Strike or the Cavalier's Vengeful Strike. These are acceptable because they are limited in scope.
In the Essentials line, class encounter powers are designed such that the player won't feel like they can be "wasted". Instead of having an attack power that is either hit-or-miss, they might:
- be an effect triggered by the player hitting with a basic attack (Power Strike causing an extra 1[W] damage) or even just by targeting an enemy (Holy Smite causing extra fixed damage, and a condition if the attack hits)
- cause half damage on a miss (Burning Hands)
- cause an Effect
- has a minor benefit on a Miss
If you adopt this style of power design, remember that the power distribution of Essentials classes is different to classic classes - there's usually only one encounter power that is improved at later levels, rather than a choice of encounter attack powers at level 1, 3, etc.