Magic and Spellcasting
Some insist that magic should be performed with ceremonial octograms, ram's skulls, and dribbly candles. Others make do with three small bits of wood and 2cc of mouse blood. In any case, unlike the specific abilities granted by most feats and tracks, spellcasting is a valuable resource for any character that values having just the right tool for the job. This comes with a drawback – spells refresh more slowly than most track abilities, so a would-be spellcaster would be wise to have a backup plan in case his magic runs out prematurely.
Magic in Legend
Mechanically, we think that a predictable and "learnable" magic system is absolutely critical. If your character wants to call fire down from the sky on the enemy, it's very important to know how big the column of fire is going to be. If you're banking on the spell working the same way it did last time, you'd better hope that a sudden change in the spell's function doesn't end up roasting your allies.
There are, of course, many game systems with a much lighter rule set, in which case it's possible to come up with a failure mode for spells that consistently advances the game's story. In a rules-heavy game like Legend, in which effects are carefully and precisely described, there is less room for ambiguous effects that can randomly screw over player characters. If you need to expand the consequences of spellcasting, look to ability descriptions that describe potential environmental effects, such as a fire spell being capable of igniting easily combustible material. If you like magic to have a more unpredictable feel, consider emphasizing rolled damage and the effects of targets' saving throws as a function of how correctly the spell was cast.