Ruby Robe

A gem robe is the pre-Hardmode magic body slot, and which stone you use only nudges the defense. The hat you pair it with is what actually changes how you play. A Wizard Hat pushes your critical rate, which suits a weapon you fire constantly and want to spike. A Magic Hat widens the mana pool instead, which is the safer pick if you keep running dry halfway through a fight. Nothing is asked of the leg slot either way, so wear whatever gives the most defense underneath.

Wear any gem robe without a Wizard Hat and Tim starts spawning underground far more often. That is the intended loop: run the robe on its own, work the caverns, and take the Magic Hat off him. Once you have it, the raised spawn rate is only an extra caster shooting at you in the dark, so switch back.

Ruby sits near the top of the robe ladder, so this one is worth making if you already have stones spare. If you do not, the same rubies go into a staff, and at that stage the weapon does more for you than a few points of defense.