FireAffinity

A genetic trait on summoned Fire Spirits. It passively grants strength charges to the unit if it ends the turn on a lava tile.

You might think this is a poor trait at first glance, since half the fire units have poor Strength. Telekinetic used to be the go-to solution to use their normal attacks, but this synergizes quite well with the Lava Girl Base Species Perks 3, which can also grant strength charges.