= 30, so that's only 23 damage.
This round, Thunderbird automatically takes47-10-5+1d6=37 fire damage
, so that's a DC 19 Fort save vs critical injury
Frenzy a second time.
1st action: Move 50', which puts Pele outside Thunderbird's reach, but keeps him inside her glaive's reach
2nd & 3rd actions: Glaive attack: 1d20+29=44, 1d20+29=47
Damage, less DR: 10d10-5=43 fire, 10d10-5=50 fire
, so that's two more crit injury saves at DC 22 and DC 25, 2 ignition checks at DC 43 and 50 (I'm assuming that once you're burning further fire damage doesn't just automatically stack), and a save or die massive damage save at DC 25.