This effect targets 1 card in your opponent's Spell & Trap Zone. (You can target either a face-up or face-down Spell/Trap Card.)[1]
The effect of this card that changes the ATK of a monster on the field is an Ignition Effect.[1]
This effect targets 1 face-up monster in your or your opponent's Monster Zone, and 1 monster in your Graveyard, for a total of 2 targets.[1]
Q&A Rulings
Q: Can I only activate the effect of "Salamangreat Heatleo" that changes the ATK of a monster on the field if that "Salamangreat Heatleo" was Link Summoned by applying the effect of "Salamangreat Sanctuary"?
A: The second effect of "Salamangreat Heatleo" can not only be activated when it is Link Summoned using only 1 other copy of "Salamangreat Heatleo" by applying the effect of "Salamangreat Sanctuary, but also if you use 2 or more FIREEffect Monsters (including a "Salamangreat Heatleo") as materials.[2]
Q: Using the effect of "Salamangreat Sanctuary, I Link Summoned a "Salamangreat Heatleo" using another copy of "Salamangreat Heatleo" as its material. In this situation, if that "Salamangreat Heatleo" is banished by the effect of my opponent's "Farfa, Malebranche of the Burning Abyss" and then returned to the field, can I activate the effect of "Salamangreat Heatleo" that changes the ATK of a monster on the field?
A: In this scenario, if "Salamangreat Heatleo" was banished by the effect of "Farfa, Malebranche of the Burning Abyss" and then returned to the field, it is no longer treated as having been Link Summoned using a "Salamangreat Heatleo" as material. Therefore, you cannot activate its second effect.[3]