You gesture at a rock troll.
The mana you were holding contributes to the spell.
You are unable to keep some of the mana from leaking out of the spell pattern.
A lance of silvery-blue light forms between your hands. Turning slightly, you throw the lance at a rock troll!
The majority of its abdomen disappears as the lance pierces its body in a spray of blood and bone and gore. Fragments of reddish-white bone pierce its skin, and one of its organs flops uselessly outside of its body.

A rock troll collapses with a heavy thud.
Roundtime: 1 second.
>look troll

You see a rock troll (dead).
The rock troll has a deeply bruised head compounded by cuts and bruises about the head, minor swelling and bruising around the neck compounded by cuts and bruises about the neck, minor swelling and bruising in the chest area compounded by cuts and bruises about the chest area, a severely bloated and discolored abdomen appears oddly rearranged compounded by a completely destroyed abdomen with nearly all flesh and bone torn away revealing a gaping hole.
It is wearing a leather cuirbouilli coat.
It is carrying a sharp pine sapling.

:)