Paragon spell - sovereign gets -5 hit points, target champion gets +1 level.  (shortened version of the spell description)

Well, so, i was trying to see if champions get any spells/abilities than what sovereign can get by casting Paragon to avoid leveling up champions the long way...  And noticed that at some point health on my sovereign stopped going down.  (Paragon became mana only spell)

Reloading the game back to before the experiment and looking at the health breakdown as well as where health was being subtracted from ... it looks like hit point cost of paragon is being subtracted from the 'base' health (which in my case was 15), after that goes to 0 (and disappears from the UI), health stops decreasing.

ex:

starting with: base=15, hardy=34, courage=5, levelUp=68

after 3 casts: hardy=34, courage=5, levelUp=68

after 10 more : hardy=34, courage=5, levelUp=68