Heroes of the Realms
SPELL SAVE DC: DC to resist a spell is 8 + magic ability mod + proficiency bonus.
SPELL ATTACK MODIFIER: Proficiency Bonus + Ability Modifier.
SPELLCASTING IN ARMOR: Requires proficiency in that armor. Wearing armor without proficiency prevents spellcasting.
CONCENTRATION: Taking damage while casting a spell forces a CON saving throw of the higher of DC 10 or half the damage received. Failing the save interrupts the spell. Normal movement and attacking does not interfere with concentration. Casting another spell which requires concentration, being incapacitated, or being killed breaks concentration.
STACKING: Spell effects stack except same spell cast multiple times (which takes highest bonus).
RITUALS: Advantage is id doesn’t consume a spell slot, but it takes longer and consumes magical components.
SPELL COMPONENTS: Typically, spells require mystic words (verbal component) and intricate hand motions with at least one hand (somatic components).
COPYING A SPELL INTO A SPELLBOOK: When you find a wizard spell of 1st level or higher, a wizard can add it to their spellbook if it is of a level for which they have spell slots and if they can spare the time to decipher and copy it.