The Elements which constitute regular matter in this Universe were specified when the Codex of Creation was written.
This Universe has all the elements which Earth has, and three extra elements which Teknall added. The gases were redesigned by Zephyrion. The three extra elements are all transition metals which occur naturally.
Mithral - a metal with similar appearance and chemical properties to silver. Structurally, it is about as strong as steel yet as light as aluminium. It has slightly above-average magical affinity.
Orichalcum - a brassy-gold metal in appearance. Structurally, it is quite mundane. However, it has one of the highest magical affinities of any of the elements. It also has decent electrical and thermal conductivity.
Adamantine - a dark-coloured metal. It is slightly more dense than steel. It is astonishingly strong structurally, with hardness rivalled only by diamond (among the pure elements), yet its higher strength in all other categories makes it an element of unmatched resistance.