Spell casting in Iron’s Spells ‘n Spellbooks works from a Spell Book, a 
Scroll or an imbued weapon, and each one uses mana and cooldowns a little differently. Once you’ve got a Spell Book in your Spellbook slot, every spell in it shows up on your spell bar, and you pick one and press a key to cast it.
The same rules apply to every spell, whichever school it’s from, so Fire Spells and Ice Spells are picked, cast and put on cooldown in the same way. What changes between them is the cast type, which decides whether a spell fires straight away, needs a wind-up or keeps going while the key is held.
Casting Mechanics
To cast from a Spell Book, the book has to be in the Spellbook slot, which is a Curios slot the mod adds to your inventory screen. Holding the book in your hand isn’t enough on its own, so if your spell bar is empty, check the book is actually equipped in that slot rather than sitting in your hotbar.
Any Spell Book will do, from a 
Flimsy Journal upwards, and the spells are written into it from Scrolls at an Inscription Table. The book’s own bonuses, like extra Max Mana, only count while it’s in that slot as well.
Selecting a Spell
Your spells show up on the spell bar near the bottom of the screen, with the selected one highlighted. By default you hold Left Alt and scroll your mouse wheel to move along the bar, or hold R to open the Spell Wheel, which lays every spell out in a circle so you can pick one with the mouse.
Once a spell is selected, press V to cast it. There are also 15 Quick Cast keys that aren’t bound to anything by default, and if you bind them, each one casts a spell straight from a slot on your bar without having to select it first, so you’ll want to bind a couple of them to the spells you use the most.
Cast Types
Every spell has one of three cast types, which decides how it fires. Instant spells go off the moment you press the key, Long spells have a wind-up before they fire, and Continuous spells keep going for as long as you hold the key, taking mana every half second until you let go or run out.
Instant
Long
Continuous
Long casts are the only type that can be cancelled by taking damage. If you’re hit by a mob or a player while one is winding up, the spell fails, although damage from burning, falling, wither, drowning and freezing won’t cancel it. Wearing an Amulet of Concentration stops any damage from interrupting you, which matters for spells like Fireball.
Mana and Cooldowns
Casting from a Spell Book costs mana, and you can’t cast if you don’t have enough for the spell. Your max mana starts at 100, and you regenerate 1% of it every half second, so an empty bar fills back up in about 50 seconds at base, and mage armor will raise how much you have.
After a spell is cast it goes on cooldown, and you can’t cast that spell again until it’s finished, though you can still cast your other spells in the meantime. The cooldown is shown on the spell bar, and it doesn’t cost any mana to wait one out, so the two limits work separately from each other.
Casting from Scrolls
A Scroll holds a single spell, and you cast it by right-clicking with it in your hand. Casting from a Scroll costs no mana at all and it ignores cooldowns, so you can use one even when the same spell is on cooldown in your book, but the Scroll is used up after one cast.
Spells that have a second cast, like Portal, can’t be cast from a Scroll, and you’ll get a message saying so if you try. For those, and for any spell you want to keep using, you’ll want to put the Scroll into a Spell Book at the Inscription Table instead, as it can then be cast as often as your mana allows.
Casting from Imbued Weapons
A sword that’s been imbued with a spell at the 
Arcane Anvil adds that spell to your spell bar while you’re holding it, and you cast it with the same key as a book spell. It costs mana just like a Spell Book does, but its cooldown is only half as long.
You don’t need a Spell Book at all to cast from an imbued weapon, so it can be used to carry an extra spell on top of the ones in your book. Each sword only holds one spell, and it works from your off hand as well as your main hand.
Boosting Casting Performance
Once you can cast a few spells, the next step is making them stronger, and that all comes down to your stats. The mod adds spell power, cast time reduction, cooldown reduction, mana regeneration and max mana, and your armor, rings, Spell Books and Upgrade Orbs are where most of those stats come from.
Spell Power
Spell power makes your spells hit harder, heal more or last longer, depending on the spell. There’s a general Spell Power stat that boosts every spell, and a separate one for each school, like Fire Spell Power, so a set of Pyromancer armor mostly makes your fire spells stronger rather than all of them.
The spell’s level matters as well, because each level adds a fixed amount on top of the base power. That’s why a higher level Scroll is worth the rarer Ink, and it’s also why the school you build around decides which armor and rings are best for you.
Cast Time and Cooldown Reduction
Cast Time Reduction shortens the wind-up of Long spells, and for Continuous spells it does the opposite and makes them last longer. Cooldown Reduction lowers the cooldown on every spell, and at 50% it cuts every cooldown in half. Past that point each extra bit does a little less, as 75% leaves a third of the cooldown and 100% leaves a quarter.
The wind-up of Long spells tapers off in the same way, whereas Continuous spells keep getting longer with no limit. The Ring of Recovery gives you 15% Cooldown Reduction and the Ring of Expediency gives 15% Cast Time Reduction, and they each need one 
Mithril Scrap to make.
Equipment and Attributes
Most of your casting stats come from gear. Mage armor gives Max Mana and school spell power, Spell Books have their own bonuses, and rings and necklaces add smaller boosts on top, like the 
Ring of Recovery. Staffs add spell power too, but only while they’re held in your main hand.
Upgrade Orbs let you add more stats to armor and Spell Books at the Arcane Anvil, so once you have a set you like, you can keep improving it instead of swapping it out. Each piece holds 3 of them through the upgrade system, and an orb like the 
Fire Upgrade Orb adds 5% spell power for its school.
Because Scrolls ignore mana and cooldowns, a few Scrolls of the spells you rely on can be kept for emergencies. If you’re out of mana in a boss fight, a Scroll can still get a heal or a big attack off when your book can’t.
FAQ
Put a Spell Book in the Spellbook slot, pick a spell on the spell bar with Left Alt and the scroll wheel or by holding R for the Spell Wheel, then press V to cast it. You can also right-click with a Scroll or use a spell from an imbued weapon.
Usually it’s because you don’t have enough mana, the spell is on cooldown, or your Spell Book is in your hand instead of the Spellbook slot. Long spells can also be cancelled if you’re hit while they’re winding up, unless you’re wearing the Amulet of Concentration.
You can, as a Scroll is cast by right-clicking with it and an imbued sword adds its spell to your spell bar on its own. Neither of them needs a Spell Book to be equipped, though a Scroll is used up after the one cast.
It makes them last longer instead of making them faster, as a Continuous spell has no wind-up to shorten. That also means it’ll take more mana in total, because the spell keeps charging you every half second for as long as it runs.
