with iskandra’s relic everytime you attack with elemental damage there is a 15% chance that the attack would be calculated as if u had an additional 325% elemental damage. The active skill will give you the base damage and the critical damage but the 400% fire/cold would have no effect.
the reason being blood orb of cthon converts the damage and then the damage modifiers applied. (to avoid double dipping)
Also going over 100% damage conversion doesn’t increase your damage as the conversions become weighting so they still add up to 100.