A centaur made out of Jello enters the arena to 60N40E. It also has two spiked chains coming out of its wrists, although they look more like tentacles than spiky chains.
Round 516: A huge armor-plated, bullet-shaped creature with a perfectly huge maw and perfectly powerful legs charges to 55N55E and tries to bite the centaur.
(You do all the rolling. Use the bulette from the MM for stats.)
It is not wise to take on an astral construct mano-a-mano.
Round 517: The bulette hits with one claw (rolled 29; best missing roll was 28) for 12 points of damage, but J-Cent heals the damage immediately (DR 12 or greater).
J-Cent smacks the bulette twice for 36 points of damage. The bulette has 20 HP remaining.
Let me know if the bulette wants to continue or bury itself in the hope of a draw.