Radiant Nashor's Tooth

The unit-level resource that gates ability casts — champions cast once their mana bar fills, so low-mana units cast more often than high-mana ones. Spear of Shojin (mana per attack) and Adaptive Helm (amplifies Mana from all sources) push casts faster, alongside starting-mana augments.

Scales with crit chance and crit damage from items like Infinity Edge and Jeweled Gauntlet. By default abilities cannot crit — the sibling Precision mechanic is what lets spell damage roll crits, so crit-on-spell builds need a Precision source before crit chance and crit damage actually apply to abilities.