You cast another Spell.
Your partially-formed Hydra grows a little more, but is still not complete.
You will need one more Creature Copy Spell to form a whole creature.
If you wish to cast this third Spell,
do so and let the Hydras fight to the death:
If your creation wins.
If your creature loses, or if you did not have enough Spells
to complete the creation,
you must decide what to do next.