fireball; ball of fire
A literal ball of fire, often used in fantasy, games, or describing a mass of flames.
The wizard launched a fireball.
A huge ball of fire rose from the explosion.
will-o'-the-wisp; jack-o'-lantern
A mysterious floating flame in folklore, often seen in wetlands or graveyards; equivalent to 狐火 or 鬼火.
There is a story about seeing a will-o'-the-wisp in the graveyard at night.
Compound of 火 (hi, 'fire') + の (no, possessive particle) + 玉 (tama, 'ball'). The reading ひのたま is a straightforward combination.