ToME4's inscription system is one of the biggest gameplay changes from traditional roguelike games. First introduced in beta 14, the inscriptions (infusions and runes) replace potions and scrolls. The design goal behind inscriptions is to eliminate the time spent by the player "farming" potions and scrolls in weak zones, in order to make a run at a tougher zone. They are unlimited in use, but have cooldowns attached, so you must carefully time your use of them to survive. Unlike many other RPGs you cannot rely on a large stack of potions to get you through a tough battle. Mastery of the inscription system is a key step towards mastering ToME4.

Inscriptions come in two flavors: runes and infusions. Runes are magical glyphs drawn on the body like temporary tattoos. Infusions are natural substances smeared/attached to the body, like nicotine patches.

The character starts with 3 inscription slots. Each slot may hold a single infusion or rune. Infusions and runes are objects that may be found in dungeons or bought in stores. Using one will add the inscription to your body, using up a free slot. If you have no free slots, then you may choose to destroy one of your existing inscriptions in order to make room for the new inscription.

Additional slots may be purchased for the cost of a talent category point, up to a maximum total of 5 slots. Category points are gained at levels 10, 20 and 30, and Cornacs also start the game with an extra category point.

You may not have more than 2 of the same type of infusion or rune. E.g. you may have 1 healing infusion and 2 regeneration infusions, but you may not have 3 regeneration infusions.

Each character starts with either 2-3 infusions or runes on its body, depending on race and class. Shaloren, Skeletons and Ghouls start with runes (1 shielding and 1 phase door), all others races start with inscriptions (1 regeneration and 1 wild) and mana-using characters also start with a manasurge rune.

Skeletons and Ghouls may not use infusions at all. Their undead bodies cannot accept nature's balms. This means they require very carefully timed use of shield runes to survive the early game. Shield runes are essential to prevent taking damage in the first place, so that healing is made unnecessary.

Characters who take the vow of Antimagic may not use runes.

Note that an alchemist's golem also has 3 rune slots (they cannot have infusions) and more can be granted through talents. You must switch control to your golem to attach a rune. Popular golem runes include shields, heat beam and acid wave.

Inscriptions work like talents: they have a cooldown period before they can be reactivated. Stunning can put your inscriptions on cooldown just as it does to talents. Some inscriptions have a duration as well as a strength to their effect, such as a rune that activates for 100 shielding over 6 turns. Some attack inscriptions have ranges of effect. Evaluating which infusion to equip can involve careful comparison of effect, cooldown, range and duration.

"Ego" inscriptions also exist, which give effects that scale with one of your stats. E.g. a brawler's healing infusion scales its Life restoration with your Strength. Sometimes they can scale much higher than regular inscriptions, making an ego relevant to your class especially desirable.

Activating an infusion gives you an effect called Infusion Saturation. Using another infusion while this effect is still active causes its cooldown period to be longer. Likewise, the Runic Saturation effect increases the cooldown periods of runes. The goal of this is to reduce "healing/regen spam" as a technique for outliving all incoming damage. Before you think But I want to survive forever! keep in mind that monsters use infusions too. If fighting an enemy who frustratingly keeps using a regeneration infusion remember that its cooldown will keep getting worse and worse as it uses it more, eventually allowing you to do sufficient damage to kill it before it heals again.

Many inscriptions take zero time to activate, giving them more flexibility on when to use in combat.