Tongues of Power
When speaking of High Magic, it is usually assumed that the Arcane Tongue is being used - first introduced to Leng by the elves, it is the safest and most commonly used tongue of power amongst humanoids. However, the humanoid races are not the only ones to devise and cast magics, and there are nonhuman traditions and tongues of power abroad in the world. With these alternate traditions come hidden magics, too - there are spells amongst the giants, ogres and dragons which have never come into common circulation amongst mortal magi.
Translating spells between magical tongues is not as simple as translating a document from one language to another. It is possible for a spellcaster to create a Draconic version of an Arcane spell (provided they know Draconic), but it requires significant research. Translating a spell is similar to researching a new one, but it costs half as much and takes half as long.
It should be noted that the words of a Tongue of Power bear little relation to the language they are drawn from. For example, Arcane is derived from Elvish, but the words of a magic spell do not have any elvish meaning. The Elvish tongue is simply the base that was used to discover certain sounds that are linked to the essential energies of the mutliverse. Likewise, though many Lower Planar beings use the Black Speech to converse, the words of a Black Speech spell cannot be used to discern what is being cast. They are "magic words", not ordinary nouns and verbs.
For this reason, simply knowing a Tongue of Power is not enough to instantly comprehend a spell written in it. Even if you know the Black Speech, it may take months to decipher the words of a Black Speech spell. This is why spells such as Read Magic exist, which serve to vastly abbreviate this process. However, knowing the language a spell is written is usually enough to identify its general purpose.
This is the "mundane" magical tongue used by most mages on Morus. The script it uses is elvish in origin, and those who can read elvish can pronounce magical words - though this does not mean that they can comprehend them. The Arcane tongue is a language to itself, composed of specific sounds that are keyed to certain cosmic forces and energies - originally discovered by painstaking research conducted by ancient elven scholars. With this formidable tool, the chaotic and wild magics previously wielded by mortal creatures could be formalised and channelled constructively.
Casting spells written in the Arcane tongue does not have any requirements or benefits beyond the usual.
The Black Speech
The Black Speech is one such tongue. A foul and evil tongue originating in the Lower Planes, learning it is trying on the sanity of even the most dedicated scholar - those who are of good alignment cannot learn it at all, for the foulness inherent in it is fundamentally abhorrent to such folk. Merely hearing more than a few words of the Black Speech spoken weakens one's sanity - non-evil intelligent beings of less than 4 HD who hear the Black Speech being spoken make a saving throw vs. death or lose 1d4 points of sanity; this saving throw is repeated for every round they listen. They must make this saving throw each round until they pass, at which point they will be rendered immune to it until 24 hours have passed.
The Black Speech is even more dangerous as a tongue of power, and is rarely used except by demons and the foul sorcerers of the lower planes. Occasionally it is found amongst powerful necromancers, the worshippers of Seidar, and the Death-Cult of Khâzath. Only evil magic-users can cast spells in the Black Speech. Saving throws against spells cast in the Black Speech are made at a +1 for evil characters, a -1 for neutral characters, and a -3 for good characters. Furthermore, offensive spells cast against good characters and defensive spells cast on evil characters are always at least 50% effective - for example, a 5d6 damage Fireball will always do at least 15 damage, and a 2d4 casting of Mirror Image will always produce at least 4 images. However, spellcasting in the Black Speech is dangerous to the caster - every time a spell is cast by a mortal, they must make a saving throw vs. death or take lethal damage equal to twice the level of the spell being cast.
Spells specific to the Black Speech are those devised by the denizens of the lower planes. They are exclusively spells of torture, pain and destruction.
The tongue of the dragon is one which is tied into the nature of the world itself. Powerfully magical beings, the dragons are more than monsters of flesh and blood; even those who never delve into the magical arts accumulate magical powers over their long life, and their most famous ability - the dreaded dragonbreath - is the direct magical expression of their will upon the world. Draconic magic is far more powerful than its mundane counterparts, though far more taxing on the spellcaster. Draconic versions of regular spells (of which there are a few) calculate damage as though the caster were 2 levels higher than he actually is. Additionally, all spells from this corpus elicit a -4 to saving throws. However, the caster must sacrifice TWO spell slots to memorize a draconic spell and, while casting, must make a successful spellcraft check or take 1d4 points of temporary and non-lethal damage per spell level as it saps his own breath; magic-users without the Spellcraft NWP always take this damage. The draconic counterparts of regular spells always eschew material and somatic components, the power being drawn from the spoken incantation and the dragon's own life force.
The tongue of the giants is not as dangerous and impressive as the formidable draconic tongue or the black speech, but is nevertheless infused with power that mortal tongues cannot muster. Giantish magic treats giantkind as "people" for the purposes of spells such as Hold Person. It also doubles any durations and trebles area of effect. However, Gigantine magic assumes a much larger reservoir of internal energy than men usually have. Only wizards with a constitution of 15 or higher can use it, and even then it deals them a number of nonlethal hp of damage equal to its spell level unless their constitution is 18 or higher.