On my own I am large,
But give me fruit,
Or an insect,
Or even a flower,
I'll grow small.
Take any letter away and rearranged,
You could have hundreds,
Maybe an instrument,
Perhaps one element,
Or even two.
What word am I?
You are a ...
dragon.
On my own I am large,
Dragons are large mythical beasts.
But give me fruit, or an insect, or even a flower, I'll grow small.
Dragon fruit, dragonflies and dragon orchids are all quite small compared to a dragon.
Take any letter away and rearranged, You could have hundreds,
Take away the o to get an anagram of grand, a thousand or "hundreds".
Maybe an instrument,
Take away the d to get an anagram of organ, a musical instrument.
Perhaps one element,
Take away the g to get an anagram of the chemical element radon.
Or even two.
Alternatively, remove the d to get argon.
The title ...
has the hint "A Monster of a Riddle". Dragons are common monsters in role-playing games, especially in Dungeons and Dragons.