Thrust.

Sauna will suffice for this.

Inferno:

Level 30

MP - 30, Damage 150%
Uses 30 MP
Lasts for 10 seconds
Hits up to 6 monsters (or players depending on skill) at once

Damage 150%

Argument x = 50

Fire Charge:

Level 30

Use 35 MP, Damage 120%, For 200 Seconds
Uses 35 MP
Lasts for 200 seconds
Hits up to 6 monsters (or players depending on skill) at once

Damage 120%
Magic Attack +38

Argument x = 1
Argument z = 100

For Inferno, x starts at 21 in level 1 and increases by 1 every level. For fire charge, I have no idea what x is for, but z starts at 13 and increases by 3 every skill level.