Anyone Can Cast Spells (via Ritual Magic) Option (OSR)

Anyone Can Cast Spells Option
For my OSR Mythos and Sword and Sorcery games I decided to come up with an option where anyone, regardless of class, can attempt to cast a spell via ritual magic. It also allows spellcasting classes a chance to cast spells of higher levels they have acquired.

The normal considerations of ritual magic apply.

For non-spellcasters to cast a Spell (or spellcasters to cast a spell above their current level or a spell not yet learned with a spell slot) the following steps must be achieved:

1. The Spell must be found or taught.
Grimoires, scrolls, writings carved on walls, mad hermits, magical lodges, etc.

2. The Spell must be in a format the caster can understand.
This could be being translated from an ancient language to one the caster understand or verbally taught by a teacher.

3. Learning how to cast the spell takes eight hours per spell level. A fifth level spell would take forty hours of study and practice to learn.

4. Casting requires time. Ten minutes per spell level. A fifth level Spell takes fifty minutes minimum to cast. The DM may require materials to be used as well.
The main cost of this type of casting is time. Time can be incredibly valuable in a dungeon or during a Mythos incident.

5. The Casting Roll.
To actually cast the Spell requires an Int check with a penalty equal to twice the Spell Level. A character with an Int of 13 attempts to cast the fifth level spell. The Spell will succeed if he rolls a 1-3 on a 1d20.

Extra casting time can increase this chance. For each full casting time increment past the minimum the caster can add a + 2 to the roll.
Four times the minimum is the most that this method can be used.
For the fifth level spell: if the time taken is 50 minutes the roll is still a 3.
If 100 minutes is taken the roll is now 5.
For 150 Minutes the roll is 7.
For 200 minutes the roll is 9.

If the Casting Roll fails:
Time and consumable materials are lost. The caster can attempt the Spell again with an additional -4 penalty to the total Casting Roll or he can wait 24 hours and avoid this penalty.

Multiple Casters:
The person leading the ritual uses his Casting Roll. For each additional caster add a +1 to the roll. The maximum bonus is equal to the Spell's level. The fifth level Spell would have a maximum of a +5 bonus no matter how many actually participated in the ritual.

Used in conjunction with extra casting time this option can really increase the chance of the casting roll's success.