Ritual Spellcasting
A trained spellcaster may attempt to cast any spell he knows (and is otherwise capable of normally casting) by performing a special ritual version of that spell. As a rule ritual spellcasting requires far more time and expenditure of materials then casting a spell normally but can be very useful when casting niche spells which otherwise would not warrant a spell slot outside of specific scenarios.

The rules for ritual spellcasting are as followed;
Choosing a Spell: A spellcaser can perform a ritual version of any spell present on their list of known spells. Prepared casters do not need to prepare a spell ahead of time to cast a ritual version of that spell.

Components: A ritual version of a spell always has verbal and somatic components and requires the use of a special ritual circle that will act as a focus. Rules for creating these circles are found below. These components are in addition to any required by the original spell - any material components of focuses must be expended and/or present when performing a ritual version of that spell.

Creating a Circle: Creating a ritual circle can be a time-consuming process. While the exact size and complexity of a circle varies from caster to caster it is a general rule the the more powerful a spell the larger and more intricate its requisite circle will be (a circle for a 1st-level spell may be a relatively simple design etched in the dirt while the circle for a 9th-level spell may consist of numerous lesser circles interwoven over each other across the floor of an entire room). A ritual circle is not crafted to a specific spell but rather a level of spell - a 1st-level Ritual Circle can be used to perform any 1st-level spell (and only a 1st level spell) as a ritual version.

The cost of creating a circle is determined by the material used to create it - a simple chalk circle will cost a few coppers while a circle drawn entirely in unicorns blood will be significantly more expensive to create. For the most part the actual materials and methods used to create a ritual circle don't have any meaningful effect on the final product but DMs can, at there discretion, determine that specific materials provide certain benefits; a circle created using powdered silver may produce spells with higher DC's when used against lycanthropes for example.

It is worth noting that a ritual circle is not consumed in the casting of a ritual spell (in much the same way as a focus component is not consumed). This allows a single circle to be used to cast multiple ritual spells - indeed many traveling spellcasters procure 'pre-made' ritual circles for there lower level spells inscribed on parchment or cloth that can be safely stored without damaging the circle (ritual circles of spell level 4th or higher are generally too large and complex to be so easily transported - though by no means impossible).

Spell Level | Creation Time | Circle Size
Level 0 | Special* | Special*
Level 1 | 10 mins | 1ft x 1ft
Level 2 | 20 mins | 1ft x 1ft
Level 3 | 30 mins | 1ft x 1ft
Level 4 | 60 mins | 5ft x 5ft
Level 5 | 80 mins | 5ft x 5ft
Level 6 | 100 mins | 5ft x 5ft
Level 7 | 120 mins | 15ft x 15ft
Level 8 | 180 mins | 15ft x 15ft
Level 9 | 240 mins | 15ft x 15ft
* Cantrips use a 1st-level ritual circle when being cast.