Valhalla Knight's Helm

There is no recipe. The whole set comes from the Tavernkeep for Defender Medals once Golem is down, which means running the Old One's Army at a tier that pays out enough medals to cover three pieces. Treat it as a straight replacement for the squire set rather than a parallel option, because there is no situation where the older one is still preferable.

The set bonus is narrow and strong. Ballista sentries fire noticeably faster, their bolts travel faster, and they punch through more targets per shot. That is a big enough change to make ballistas the default sentry for the rest of Hardmode instead of one of four choices.

The second half is a panic button you do not press. Taking damage triggers a short buff that roughly halves the reload on every ballista you have out. So the set rewards standing in the fight rather than retreating from it, which lines up neatly with the defense it hands you.

No other summoner set in the game comes close on defense, not even Vortex armor, and it carries strong passive health regeneration on top. Stardust armor is the higher tier and is nowhere near as durable, so there is a real case for staying in this past Moon Lord in fights where you expect to eat damage.

The regeneration stacks with other sources, including the squire helm and a Shiny Stone. Duck out of a fight for a few seconds and you return close to full, which changes how you approach boss patterns you cannot completely dodge.

Melee bonuses exist but are thin: some damage on the helm, some critical chance on the greaves, nothing else. Do not build a sword loadout around this. Whips are the natural fit, since they scale off the summon damage the set piles on.

The chest piece alone has the largest summon damage bonus of any single item in the game, ahead of the Red Riding Dress, the Dark Artist robes and the Stardust Plate. Combined with its defense and regeneration it slots into other builds well, at the cost of whatever set bonus you give up.

Its rivals each do something it does not. The other two robes also boost non-summon damage, and the stardust chest carries minion-specific perks, so all three can out-damage it inside a dedicated build. This one wins on staying alive.

Because summon bonuses apply to sentries and regular minions alike, pairing this with a Pygmy Necklace, Necromantic Scroll and Papyrus Scarab turns it into a full army. That is at its best during invasions and stationary boss fights, where sentries being rooted in place costs you nothing.

Set against Beetle armor with the defensive chest, this trades damage reduction for regeneration and a better average melee bonus. Beetle wins when hits are rare and heavy, because its stack has time to rebuild between them. This wins when hits are constant, because regeneration never switches off while beetle's stack gets stripped down and never recovers. Events with wall-to-wall enemies are exactly that case, and the extra sentry slots help there too.

Valhalla is the Norse hall where warriors chosen off the battlefield spend their afterlife training for Ragnarok. Half of the honored dead go there; the other half go somewhere else entirely.