Five

a random little piece; i'd be interested in any guesses as to what i'm talking about

Five

Four tall and powerful trees,
One fat, crooked trunk.
Four long and spidery legs,
One, cut off, is short.
Four muscular training soldiers,
One old general, still stronger.
Four sky bound towers of stone,
One small keep, impenetrable.
Four Goliaths, taunting all,
One brave David fells them.