Spells: Myra can cast a total of 3 spells by the end of Underscorch, each doing something different and each costing a different amount of Mana. She doesn't learn her first spell until the Papyrus Fight(or right after in the Geno route) and learns her last before the Sans encounter in New Home. See the spells at the very bottom. Mana: You generate 1 Mana each turn(Mana cap scales with LV) but some equipment or items can make you generate more mana. 50% of excess Mana at the end of battle(referred to in the story as Overbled Mana) is turned into a small boost for how much G you win (roughly 1 G per 3 Mana) while the other 50% of Overbled Mana transfers to the next battle. (Papyrus Teaches)Masquerade: Increase DEF for 3 turns, Cost: 4 Mana (Tyr Teaches)Minor Restoration: Recover 6 HP, Cost: 3 Mana (Flowey Teaches)Willed Swap: Can change attack colors for 1 turn, Cost: 10 Mana
Underscorch by me