Using Psionics (POSP)

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Psionic energy can be shaped and used by psionicists and wild talents to produce desired effects, called psionic powers. All psionic powers are grouped into one of five categories, or disciplines, based on how the energy is used. The major powers of a given discipline are called sciences.
Two key concepts need to be presented before the rules for using psionics in the AD&D game are detailed. These are psionic strength points (PSPs) and mental attack rolls (MTHAC0s). These are described below.
Psionic Strength Points (PSPs): Every psionic character has an internal store of psionic energy, represented as psionic strength points. These are used to activate sciences and devotions, to focus psionic attacks, and to determine how much psionic damage a hero's psionic defenses can stand.
Mental Attack Rolls: The success of psionic attacks against closed minds is determined by the number a character needs to roll on 1d20 to hit a specific mental armor class (MAC). The mental attack number (MTHAC0) is the number the character needs to hit a MAC of 0. When used on open minds, the roll is made against a power's MAC. Each power has a base MAC number used to determine the difficulty of activating a psionic power against an open mind.
All psionic powers belong to one of five disciplines: clairsentience, psychokinesis, psychometabolism, psychoportation, and telepathy. Within each discipline, the powers are divided into two categories: major powers, or sciences; and minor powers, or devotions. The five disciplines are defined as follows:
Clairsentient powers allow characters to perceive things beyond the natural range of human and demihuman senses.
Psychokinetic powers move objects across space using only the energy of the mind.
Psychometabolic powers affect the user's body by altering it in some manner.
Psychoportive powers allow psionic travel, moving characters from one location to another without crossing space.
Telepathic powers involve the direct contact of two or more minds.
==Closed and Open Minds==
The minds of all characters and creatures exist in one of two states: either closed or open. A closed mind has either natural or enhanced defenses that protect it from unwanted intrusion. Only those things that enter through the normal senses (such as sight, sound, taste, touch, or smell) can impact on a closed mind. The minds of all characters and creatures are naturally closed. A character can voluntarily open his or her mind to psionic contact, or a closed mind can be opened by psionic attack.
An open mind is not a natural state. For a mind to be open, psionic defenses must be voluntarily lowered (in the case of a willing subject) or breached by psionic attack (in an unwilling opponent). A psionicist's own mind is considered open when using a psionic power with an area of effect of “personal” (such as the heightened senses devotion).
==Mental Armor Class (MAC)==
All characters and creatures have mental armor classes (MACs). While physical Armor Classes protect a body from physical attacks, MACs provide protection from psionic attacks. The MAC rating ranges from minimal defense (MAC 10) to maximum defense (MAC –10); there are no MACs worse than 10 or better than –10.
As with standard Armor Class, the higher the MAC number, the more vulnerable the character is to psionic attack. Likewise, with all attacks, a roll of 20 always hits and a roll of 1 always misses, regardless of the target's MAC number.
For those who have copies of The Complete Psionics Handbook and who want to continue using the “optional results” rules (page 28), make the following change. A roll of a power's MAC score gives the good result (what used to be signified by a roll of the power score), while a roll of 1 gives the bad result (what used to happen on a roll of 20).
To determine a base MAC number, find the character's Wisdom score on Table 74 below. Then find the character's Intelligence score and add the indicated MAC modifier. MACs can be improved through proficiencies and other means, as detailed later.
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 Table 74: Base MAC and PSP Bonuses
AbilityScore	BaseMAC	MACModifier	PSPBonus
15 or less 	10 	0 	0
16 	9 	–1 	+1
17 	8 	–1 	+2
18 	7 	–2 	+3
19 	6 	–2 	+4
20 	5 	–3 	+5
21 	4 	–3 	+6
22 	3 	–3 	+7
23 	2 	–4 	+8
24 	1 	–4 	+9
25 	0 	–4 	+10
Example: Tylk of the Westwoods has a Wisdom score of 18, which yields a base MAC of 7. He has an Intelligence score of 16, which gives a modifier of –1. Without other enhancements, Tylk has a MAC of 6 (7–1 = 6).
==Psionic Strength Points (PSPs)==
Every psionicist and wild talent character has psionic strength points, or PSPs. In many ways, PSPs are like mental hit points, though with a different function. Not only do they determine a character's current psionic strength, they also power psionic abilities. This mental strength is used to create psionic attacks, activate psionic powers, and keep psionic defenses in place. As long as any PSPs remain, psionic defenses keep the mind closed to psionic intrusion of any sort. When a psionic character's PSP total falls to zero, his defenses crumble and his mind is left open to psionic contact.
Each time a character uses (or attempts to use) a psionic science, devotion, or attack, he must pay the listed cost from his current PSP total. Damage caused by psionic attacks is also subtracted from PSP totals.
The PSP total for a psionicist depends on four factors: the psionicist's Wisdom, Intelligence, and Constitution scores, and his experience level. Together, these factors determine the psionicist's PSP pool. A 1st-level psionicist automatically gets 15 PSPs. This number is modified by bonuses granted by high ability scores. Lastly, the psionicist rolls 1d6, which is added to generate a PSP total.
The PSP total for a wild talent is determined with slight modifications. A wild talent automatically receives enough PSPs to use his power (or powers) once. In addition, he gets 10 PSPs (instead of 15) and any bonuses granted for high Wisdom, Intelligence, and Constitution scores. He also rolls 1d4, instead of 1d6.
Example: Tylk of the Westwoods has a Wisdom score of 18, an Intelligence score of 16, and a Constitution score of 17. At 1st level, he gets 21 PSPs (15 + 3 + 1 + 2 = 21) plus a 1d6 die roll. Garon, a wild talent with the same ability scores, gets 16 PSPs (10 + 3 + 1 + 2 = 16), a 1d4 die roll, and enough PSPs to use his psionic power once.
===Gaining PSPs===
The PSP total of psionicists and wild talents increases with every level advancement. Psionicists receive 1d6 PSPs with each level increase up to 9th level, plus any bonuses for high Wisdom, Intelligence, and Constitution scores. Starting at 9th level, psionicists gain just 3 PSPs, and they receive bonuses only for high Wisdom scores. Regardless of their Intelligence or Constitution scores, they no longer receive bonuses for these abilities. Wild talents, on the other hand, receive only 4 PSPs at each level increase, regardless of their level. Further, no die rolls or additional modifiers are applied.
Example: The psionicist Tylk of the Westwoods has a Wisdom score of 18, an Intelligence score of 16, and a Constitution score of 17. When he advances from 1st to 2nd level, he receives 1d6+6 PSPs: the automatic 1d6 die roll and a +6 bonus for his high ability scores.
===Recovering PSPs===
Characters recover expended PSPs by resting for specific lengths of time (minimum of one full hour). The only states of rest that allow for PSP recovery are sleep or meditation. Any other physical activity or the use of psionic powers (which expend PSPs) negates the recovery process for that hour. A character can never recover more PSPs than his maximum total.
During each hour of rest, characters recover one-eighth of their total PSPs (bearing in mind that they never recover more than their maximum total). To do this, divide a character's PSP total by eight and round up. This is the number of PSPs the character recovers after one full hour of rest. So, if a psionicist is reduced to 0 PSPs, it takes eight full hours of rest to recover the expended PSPs—regardless of whether he has 20 or 100 PSPs.
Example: Neecha Nightmoon has a total of 48 PSPs, and she has lost 24 of them during a recent psionic battle. After an hour of sleep or meditation, Neecha can recover 6 of the expended PSPs (48 ÷ 8 = 6). She is now at 30 PSPs.