It can be socketed into Weapons and Shields. It can only be inserted into Inferno or Meta rune slots.
Trelos is one of the Runes available in Lords of the Fallen (LotF). Trelos is a rune that increases the rate of ignite buildup for weapons and enhances resistance to ignite for shields. It reflects the deadly nature of some Rhogar weapons.
While the heat of some Rhogar weapons is such that an inflicted wound might be instantly cauterised, the victim is rarely alive long enough for it to matter.
Lords of the Fallen Items