Starting Hit Points. Everybody’s starting hit points are equal to hir Constitution plus what ze rolls on the first hit die. This is in place of the character’s CON bonus, and it only applies at 1st level.

Dwarves and Gnomes. Dwarves and Gnomes have Magic Resistance 0, and can take increased Magic Resistance as a Racial Feat for MR 5. The ability cannot be stacked.

Notes about Skills

Ritual Caster feat: Artes Liberales. Instead of the listed purpose of the 5E Feat Ritual Caster, the feat allows you to use hir Arts to read and cast rituals. If the character is not proficient in the necessary Arts, ze can read and understand rituals but has no ability to cast them.

Arcana: Magic Theory. Magi use this skill when performing laboratory work: studying and creating spells, crafting elixirs and magic items, and otherwise developing their mastery over magic in non-spellcasting avenues. For non-spellcasters, this skill gives them skill to support magi in laboratory work.

Ancient Languages. The Language proficiency lets a character learn ancient languages, just as any other language. For magi, this helps them immensely when recording or learning magical spells and primers. For mundane characters, this allows them to read and write the same texts.

Additional Feats

Magical Training. The character has spent extensive time studying magical forms and techniques.
Ze gains proficiency in 3 Arts at Magnitude 1. Don’t forget to take at least one Form and one Technique!
Ze also learns 30 levels in Spells for any Arts ze can use. Ze gains Magic Resistance of 0, if ze doesn’t have it already, and ze can cast and use magic.

Magical Development. Requires: Magical Training. The character makes an effort to train hir magical knowledge. Ze gains 1 magnitude in additional Arts and 20 levels in Spells for Arts ze can use.

Magical Virtue. The character gains a minor virtue from the Hermetic or Supernatural categories in Ars Magica, with DM approval.

Ritual Caster. If the character is a spell caster, ze can read and cast rituals using hir Arts.
Otherwise, the character reads and understands rituals and can assist in their preparation and execution, but cannot cast them.