Alright, you might think I'm odd for posting a strategy article on a spell. However, I found that the Lion Clan can utilize this spell better than most any other clan in the game. Let's see what it does:

-Fires of Purity
*Spell*
3 Gold
Open Elemental: Bow this Shugenja to add a 3F/3C bonus to one personality with an Honor of 3 or higher until the end of this turn.
3 Focus

Alright, so first we can obviously see that this spell can be bought off of the Lion Stronghold as it has the 3 gold cost which seems to run rampant in most Lion Decks. Now we see it's ability to give a +3/+3 bonus to any personality with 3 or more personal honor. Which Lion personalities have 3 personal honor or above?

Matsu Gohei (1/3 +2F when attacking)
Ikoma Kimura (0/2 Bow an honor producing holding and him to rehonor any personality)
Ikoma Ujiaki (2/4 Dishonors opposing personalities when one of yours dies)
Akodo Kage (0/4 Bows to give +1+1 Sensei tokens, 2 maximum per personality)
Matsu Turi Promo. (1/3 +2F when attacking)
Ikoma Gunjin (0/4 Tactician)
Ikoma Gunjin Exp. (1/5 Tactician +2 to Focus values on Tactician)
Ikoma Tsanuri (3/3 Tactician Terrains have no effect)
Ikoma Tsanuri Exp. (5/4 Tactician When defending you may bow her to send home opposing unit with less force)
Ikoma Isanuri Exp. 2 (5/4 Tactician Bows to destroy opposing unit with less force)
Matsu Tsuko (6/5 Tactician)
Matsu Tsuko Inexp. (4/3 Adds Personal Honor to Chi or Force)
Kitsu Motso (2/4 Allows you to take two consecutive actions)
Kitsu Motso Exp. (2/5 Tactician Can get Terrains from your deck and put them into play)
Kitsu Motso Exp. 2 (3/5 Moves Lion personalities in if you have less personalities in the battle)
Matsu Agetoki Exp. (5/5 Gives another cavalry unit +2+2)
Ikoma Ryozo (3/2 Goes home from battle when favor is used)
Matsu Daoquan (1/1 Gets +2+2 if you have the least honor)
Akodo Matoko (4/3)
Akodo Toturi Inexp. (5/5 Tactician Straigtens followers in his unit)
Ikoma Yosei (2/3 Allows you to play terrains even if you aren't in the battle)
Matsu Domotai (1/3 Gets force for each other Lion personality in the same battle, may not exceed chi)

I believe that about covers it. As you can see, Lion have *a hell of a lot* of guys with 3 personal honor or higher. In fact, we boast the most personalities with this kind of honor in the game.  Strength of Purity is utilized in litteraly any Lion Military deck out there. This spell is a re-useable Strength of Purity, making it an assured force bonus. The Lion have a few shugenja out there (most notably Kitsu Sanako, and Kitsu Okura as they fit the Lion gold scheme). With a 3 focus it goes towards any Tactician bonus, (3 more force, am I beginning to see a trend?) and it can also go towards that full priced Morishigi with Merchant Caravans.

*OVERVIEW*

-Lion Clan has the most personalities with 3 Personal Honor, making this an effective force booster.

-Also adds that +3 Chi

-An INFINITE force booster (unless the Shugenja is destroyed)

-3 gold, fits the Lion Gold Scheme PERFECTLY!

I hope you find a place in your deck for this forgetten spell, it can prove very useful.

-Matsu Kusinagi