Imskir Iron-Eater

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)
When Imskir enters, you draw X cards and you lose X life, where X is half the number of artifacts you control, rounded down.
{3}{R}, Sacrifice an artifact: Imskir deals damage equal to the sacrificed artifact's mana value to any target.

Modern Horizons 3

Affinity for artifacts (This spell costs {1} less to cast for each artifact you control.)
When Imskir Iron-Eater enters the battlefield, you draw X cards and you lose X life, where X is half the number of artifacts you control, rounded down.
{3}{R}, Sacrifice an artifact: Imskir deals damage equal to the sacrificed artifact's mana value to any target.

Affinity for artifacts
When Imskir Iron-Eater enters the battlefield, you draw X cards and you lose X life, where X is half the number of artifacts you control, rounded down.
{3}{R}, Sacrifice an artifact: Imskir deals damage equal to the sacrificed artifact's mana value to any target.

Modern Horizons 3 Promos

If an artifact on the battlefield has {X} in its mana cost, X is 0 when determining its mana value.

The value of X is calculated only once, as Imskir Iron-Eater's triggered ability resolves.

Use the mana value of the sacrificed artifact as it last existed on the battlefield to determine how much damage is dealt.