Goblin Battle Standard

The event turns up on its own eventually, but you usually want the Goblin Tinkerer long before that. Summoning it yourself skips the wait and gives you a repeatable source of spiky balls at the same time. Somebody in the world needs a decent health pool before the game will accept the summon, so it is not a first-day tool.

The scouts that carry it wander the far left and right edges of the map, well past where most players build. Collecting enough for several standards means deliberate trips to the world edges rather than hoping one wanders past your base.

Warlocks join the invasion once the world turns, and they carry the shadowflame weapons. On demand summons are by far the fastest way to farm those, so it is worth banking a stack of standards before you break the altars.