To determine Charlemagne's HP at level ten, we need to know the rate at which his HP increases per level. You mentioned that his HP increases by the level he is going to, so at level two, his HP would increase by two, at level three by three, and so on.
Using this information, we can calculate Charlemagne's HP at each level:
Level 1: 626 HP
Level 2: 626 + 2 = 628 HP
Level 3: 628 + 3 = 631 HP
Level 4: 631 + 4 = 635 HP
Level 5: 635 + 5 = 640 HP
Level 6: 640 + 6 = 646 HP
Level 7: 646 + 7 = 653 HP
Level 8: 653 + 8 = 661 HP
Level 9: 661 + 9 = 670 HP
Level 10: 670 + 10 = 680 HP
Therefore, Charlemagne would have 680 HP at level ten.