If you look at the map, the middle region where the elements are states low levels, starting from 0 for the oracle (center) and around 10-15 at the element palaces, slowly growing as you move further out. You can only reach 80 at the far left corners (on the right goes to 65 only), while buffed opponents with 1000HP would be level over 100.
Which means you need to seek the high levels at the far fringes of the map, and the 1000HP may not even be possible, or only with very bad other stats (no ups, too few cards, no double draw or mark).