Deltarune does not let you build a character. Your party is fixed, their spells are fixed, and Kris cannot be reclassed into a mage no matter how badly you want it. What you actually control is equipment, armour, and how you spend Tension, and those three decisions change fights more than they look like they should.
So this is an equipment and party guide wearing the word "builds", because that is what the game gives you.
Tension is the whole combat system
TP fills the bar at the top of the screen. You gain it by grazing bullets, passing close to attacks without being hit, and by defending. You spend it on every spell in the game.
That creates the central loop: play a dangerous defensive turn to earn the Tension that pays for the powerful offensive one. Players who defend safely at the back of the bullet board earn almost nothing and then wonder why they cannot afford Rude Buster.
Grazing is the skill worth learning. Sit near the bullets, not away from them.
Defending also gives TP, so a turn where nobody has anything useful to do is never a wasted turn.
Armour is shared, weapons are not
Each character has one weapon slot and two armour slots. Weapons are character-specific. Armour is not, and this is where the actual decisions live.
Armour in Deltarune rarely just adds defence. Pieces grant TP on defend, raise magic, change how much Tension you generate, or trade defence for offence. Two armour slots per character across a four-person party is eight decisions, and they are the closest thing the game has to a build.
The general rule: put defensive armour on whoever is drawing damage, and TP-generating armour on whoever is casting. Ralsei wants to afford Heal Prayer every turn. Susie mostly wants to survive being Susie.
The party, and what each one is for
Kris is your flexible slot. Average across the board, and the only one who can use most of the special weapons the game hides.
Susie is damage and nothing else. Rude Buster costs a lot of TP and hits hard, and Susie will occasionally decide to attack instead of following your order, which is a character trait rather than a bug.
Ralsei is healing and Pacify. Heal Prayer keeps the party alive; Pacify is how you end fights without killing. He is the reason the pacifist route is possible at all.
Noelle brings IceShock and, more importantly, the ability to freeze. Her spells scale in ways the others do not, which becomes very relevant on one specific route.
Recruiting is the reward loop
Sparing enemies instead of defeating them recruits them to Castle Town. Recruits open shops, add content, and change the town between chapters.
To spare, you ACT until the enemy's name turns yellow, then use Pacify or MERCY. It costs more turns than killing does, which is the trade: the pacifist route is slower and gives you a town.
If you are playing for content rather than speed, recruit everything. Missing a recruit means missing a piece of Castle Town that never comes back for that save.
The Weird Route exists and you should know before you start it
There is an alternate path in Chapter 2 built around Noelle and her ice magic. It is not a difficulty mode. It is a deliberately unpleasant sequence that changes the story, and the game makes it clear it disapproves.
It requires specific, non-obvious actions and cannot be stumbled into by accident. It also locks out content on that save file.
Play the normal route first. The Weird Route is more interesting when you know what it is displacing, and it is not a route to run on your only save.
Secret bosses reward the equipment hunt
Each chapter hides an optional boss well beyond the normal difficulty curve, and beating them yields the best equipment in the game to that point.
They are the reason to care about your armour choices at all, because the standard encounters do not demand optimisation and these do. If the regular game feels too easy, this is where the difficulty is kept.
The Deltarune walkthrough covers the chapters in order.
