Here's how I think it'll work. This is the multiclass wizard:
Level 1: 1d4HD, MA+2, WA+0, Spell DC 10+INT, Arcane Magic, Spellbook
Level 2: 2d4HD, MA+2, WA+0, Spell DC 10+INT,
Level 3: 3d4HD, MA+2, WA+0, Spell DC 10+INT, Cantrips
Level 4: 4d4HD, MA+3, WA+0, Spell DC 11+INT,
Level 5: 1d4HD, MA+3, WA+0, Spell DC 11+INT,
Spell power (based on total level)
Level 2: 1 1st level spells
Level 3: 2 1st level spells
Level 4: 3 1st level spells,
Level 5: 4 1st level spells, 1 2nd level spells
Level 6: 4 1st level spells, 2 2nd level spells
What does it mean?
A 3rd level fighter multiclasses in wizard. She gets:
a 1d4 HD
+0 to Weapon Attacks
+2 to Magic Attacks when casting wizard spells
the ability to cast Arcane Magic
A Spellbook
3 1st level spells casted as a 4th level wizard with a DC of 10+ her INT mod
Level 1: 1d4HD, MA+2, WA+0, Spell DC 10+INT, Arcane Magic, Spellbook
Level 2: 2d4HD, MA+2, WA+0, Spell DC 10+INT,
Level 3: 3d4HD, MA+2, WA+0, Spell DC 10+INT, Cantrips
Level 4: 4d4HD, MA+3, WA+0, Spell DC 11+INT,
Level 5: 1d4HD, MA+3, WA+0, Spell DC 11+INT,
Spell power (based on total level)
Level 2: 1 1st level spells
Level 3: 2 1st level spells
Level 4: 3 1st level spells,
Level 5: 4 1st level spells, 1 2nd level spells
Level 6: 4 1st level spells, 2 2nd level spells
What does it mean?
A 3rd level fighter multiclasses in wizard. She gets:
a 1d4 HD
+0 to Weapon Attacks
+2 to Magic Attacks when casting wizard spells
the ability to cast Arcane Magic
A Spellbook
3 1st level spells casted as a 4th level wizard with a DC of 10+ her INT mod