Ignite

Ignite is a simple spell used to ignite different kinds of lightsources. While it can be misused to cause horrible fires - indeed there are reports that some fires in cities of Britannia originated that way - its main purpose is to ignite lightsources like candles, torches or braziers, in case that the caster has no means at hand to ignite it manually. However, this only applies to one single lightsource. Douse is its opposite spell.

In Ultima IX, this spell is needed for the ritual of binding, which is used to bind spells permanently to a spellbook, as the candles on the pentagram can only be ignited with it.

If every lightsource in sight is to be ignited, the Great Ignite spell is needed.

Ultima Saga
In Lynn Abbey's Ultima Saga, the linear spell of hearthfire creates sparks which can easily ignite most flammable materials. The mage need only coat their fingertips in greenwood ash and expends a small amount of mana. Linear spells do not use words of power or traditional reagents, and do require mana.

Trivia

 * In Ultima VII, this spell is redundant, as everything can be ignited with a double-click.
 * This perhaps is the most used spell in Ultima IX, right next to Douse.