Monster movement example:
A Troll at full health attacks the Wall, destroying the Wall and taking 1 point of damage.
A Troll at full health attacks the Wall, destroying the Wall and taking 1 point of damage.
The Troll stays in the Swordsman ring.
On Phase 5 of the next turn, the Troll moves INTO the Castle ring, destroying
the Tower and taking 1 point of damage
On Phase 5 of the following turn, the Troll moves 1 space clockwise, destroying the Tower in that space and taking its final point of damage.