Problem with Zelgius

Anyone saying they have a problem with Zelgius just needs to stop right there. You can build any IV Zelgius and still run a powerful unit, even with a -ATK bane. If you want him to be speedy, run his base kit for black Luna and panic ploy, and then either run a speed seal with fury or you could even run life and death to bring him to 38 speed (not recommended due to the def loss). Otherwise, run him like a proper tank. You can run his base kit with QR in the B slot with the heavy blade seal which would allow him to fire off black Luna every enemy phase he’s above the threshold. He can be great in mixed teams as well if he runs with attack buffers to ensure heavy blade will trigger. The budget option would be to run him with his base kit and slap the QR seal on him. He’d still be a hard hitter. Another possibility is to run distant defense in A and as a seal (or mix close defense in for full coverage) so he becomes a fully ranged tank with better mage coverage. There’s a lot of possibilities for Zelgius. Just be happy you got one.

I agree with TG15, a -spd Zelgius still has 30 speed which is better than most units to have. With a 41 def, your Zelgius is basically a speeder Arden who can DC on almost any range unit.

Now for builds, Zelgius can use:
(A) distance/close def., steady breath (overrated honestly)

(B)vantage, wary fighter, bold fighter(with steady breath that unit will be hell to go against), guard might be good to counter steady bold combo, seal atk/def 2 is actually good too.

(C)ward skills, armor march, drive skills, threaten skills, panic ploy (only useful when teams use fortify and rally skills)

(S)distance/close def, QR

Now for sheild skill i would use any movement skill for versatility or harsh command for debuffers.