Pyromantic Pact

Replace your mana with Infernal Flame.
As you use skills, you accumulate Infernal Flame, which can then be used to deal fire damage based on your Maximum Life + Energy Shield.
The main downside is that you’ll lose 10% of Infernal Flame per second if you’re not gaining it, but this is mitigated by other passives like Bringer of Flame.
Bringer of Flame

Enhances all damage, including that of Path of exile currency your minions, making Ignite Chance and Magnitude more potent when your Infernal Flame is not low.
This node will boost Ignite builds, making it a must-have for those focusing on DoT fire damage.
Summary
Bloodmage is the better choice for crit-based caster builds and can provide superior survivability with Life stacking. It also opens up the potential for high damage output through Gore Spike and life sustain through Vitality Siphon.

Infernalist excels in damage over time and minion synergies. With Demonic Possession, Loyal Hellhound, and Pyromantic Pact, it offers more versatility, though it requires careful management of resources, especially the Infernal Flame mechanic.

Both Ascendancies offer powerful builds, with Path of exile currency for sale Bloodmage leaning towards crit and tackiness, while Infernalist leans into DoT and minion-based playstyles. Ultimately, your choice will depend on whether you prefer crit-based damage or the explosive potential of DoT and minions.