Mistvault Bridge

Mistvault Bridge enters tapped.
Indestructible
{T}: Add {U} or {B}.

Galvanic Blast

Galvanic Blast deals 2 damage to any target.
Metalcraft — Galvanic Blast deals 4 damage instead if you control three or more artifacts.

Drossforge Bridge enters tapped.
Indestructible
{T}: Add {B} or {R}.

Enchant artifact
Enchanted artifact is a creature with base power and toughness 5/5 in addition to its other types.

Silverbluff Bridge enters tapped.
Indestructible
{T}: Add {U} or {R}.

Destroy target land. Its controller may search their library for a basic land card, put it onto the battlefield tapped, then shuffle.
Draw a card.

Destroy target land you control and target land you don't control.

({T}: Add {U} or {R}.)
As Steam Vents enters, you may pay 2 life. If you don't, it enters tapped.