If you initiate for a second title, then here are the constraints:
1. Any spell you learn as a result of that title is divided by two, and the division is applied after all other operations, except plane mastery. If your secondary title is lord of buckets, then your spell, bucket of doom which you spent 10 points on, will have its effect cut in half to 5.
2. You recover power of the colour of your secondary title as well as your primary title
3. All titles aside from your primary title are considered secondary titles and are not exclusive.
4. No spell learnt from a secondary title can be greater than your current number of initiations + 5. If you have 6 initiations, you can only learn a spell up to 11. You can modify this by taking constraints and advantages (but note 1).
Ex.
Nightshade, the Lord of Darkness has a secondary title: the Caller of the Void. He decides that he wants a spell that damages someone by exposing them to the void. He takes out some time to learn it. He sacrifices appropriately, learns the spell and calls it Kiss of the Void. He decides that he will learn the spell at 80, and takes the 'ritually pre-cast' constraint, to take it to 240. He doesn't want it to be a bolt or a ray, so he chooses a standard seeker deployment, with no modification. This means that the effect will travel at about half the speed of a bolt spell, but it will chase the target for a couple of rounds.
He doesn't want any advantages. Single target seeker is good enough for him, so he stops there.
Now he applies any adders that he might have: He has a gauntlet with an onyx in the palm that adds 5 to the effect of all his spells, he has one or two others, but they only apply to darkness magic and so cannot be used. His final force value is 245, which is a beautiful number, full of justice and vengeance visited upon the sinful.
Now, he halves the value, dropping all factions. The final force is 122. Ah, well.
5. Spells from your secondary title cannot be improvised, they must be learnt beforehand, even if the title is an elemental one.
These spells must be stored in a spell rack. Obviously, this means that you can get the benefit of the bonus for 'ritually pre-cast' spells (but, again, note 1). So,
6. If you initiate for a secondary title, then you can use a spell rack.
Now, there are some issues with spell racks. Well, more accurately, there are issues with metal armour. Cloth or leather armour causes no problem, but metal armour empties matrices in all spell racks the wearer is carrying. To find out how many matrices are effected, divide your armour value by 3 and drop all fractions (yay, you say, finally a truncation in the player's favour...but wait, there's more).
If the armour is chain, you use the least armour value. If your armour is plate, you use the highest armour value. Obviously, if your armour is all the same, then there's no difference.
Ex.
Thaniel's chain mail is 10/8/10, so he divides 8 by 3 and truncates, getting 2. He has 3 spell racks, a rosary containing 4 spell matrices, a psalter containing 3 spell matrices, and his sword containing 1 spell matrix.When he gets into his armour, within minutes each spell rack fades until his rosary now only holds 2 spells and his psalter holds only 1 spell. His sword is a lump of steel with an edge.
Rook on the other hand, wears plate mail 10/16/8. He divides 16 by 3, truncating and gets 5. He decides that these spell racks are too small and fiddly for his big dwarf fingers and goes off to hit something squishy. Like a spell caster.
If you have a great ring of power, there seems little point in initiating for a secondary title of that ring i.e. initiating for the Lord of Cats when you have the Great Ring of Cats. Well, except you'd probably have more spell matrices, I suppose.