Cookies
Ah, cookies. Soft chewy goodness with a hint of chocolate. Cookies are special rewards that I might give people for outstanding role-play, and excellent idea, or just because I feel like a nice guy. Cookies are a sign of above and beyond performance and a token of my appreciation. They're also extremely handy, in game. Using a cookie in-game does not require an action. If you have a cookie, you can do any one of the following things:
Eat the Cookie. If you decide to eat your cookie, then your character is healed of all hit point damage they may have taken this round, and they ignore all damage until the start of their next turn. This does not heal your character to max HP. You just take no damage this combat turn.
Force a Re-roll. You can expend the cookie to force any player, including yourself or the DM, to re-roll any d20 roll.
Trade the Cookie. You can give your cookies to other players if you so choose. You can give them away, or you can trade them for services rendered in game. Heck, you can trade them for services rendered out of game if you like, although why anyone would trade something real for a virtual cookie is beyond me.
Activate a Class/Race Feature. You may use a cookie to activate a limited class or race feature, such as a bardic inspiration or racial spell.
Ability Score Increases
Ability score increases are no longer awarded by your class, but instead by your total character level. You receive an ability score increase at 4th level, and every 4 levels after (4th, 8th, 12th, 16th, and 20th). Fighters explicitly gain additional ability score improvements at 6th, 14th, and 19th level.
Mana
As opposed to the Vancian magic system of spell slots, all characters will gain mana, which they can use to cast spells. All characters have mana, even if they lack the Spellcasting class feature. You gain mana based on the number of Spell Dice you posses, which is a number of 1d6 equal to your level. (Starting in this game, you'll have 3d6.) If you have the Spellcasting class feature, add your spellcasting ability score to each die. (Example: If Charisma is your spellcasting modifier, and you have a Charisma of 16, you would gain 3d6+9 at 3rd level.) Much like rolling your hit points at each level, you also roll your spell dice to create your over-all mana pool (mp). Alternatively, you may gain maximum mana at first level (6), and can take the average (3) each level after.
Casting Spells. Your spells known/prepared per day do not change. Instead, you can cast any spell you know by expending the requisite number of points from your mana pool. Cantrips ♦ 1 mana; 1st ♦ 3 mana; 2nd ♦ 5 mana; 3rd ♦ 7 mana; 4th ♦ 9 mana; 5th-Level ♦ 11 mana; 6th ♦ 13 mana; 7th ♦ 15 mana; 8th ♦ 17 mana; 9th ♦ 20 mana.
Increasing a spell's level. If a spell has the option of being cast with a higher-level spell slot to increase its effect, you may instead expend the appropriate amount of mana to do so. For example, a 4th-level fireball cast would cost 9 mana, and would deal 9d6 points of fire damage. You are still required to be able to cast 4th-level spells to do so.
Regaining Mana. During any short rest you may expend any number of Spell Dice to regain lost mana. Roll the desired number of 1d6 and add that amount to your mana pool. You regain expended Spell Dice and completely refill your mana pool at the end of a long rest.
Mana and Sorcery Points. When you gain the Font of Magic feature, Flexible Casting instead lets you convert sorcery points to mana and vice versa. For every 1 sorcery points spent, you add 1.5 mana to your mana pool, rounded up to the nearest whole number. For example, 2 sorcery points would create 3 mana, while 3 sorcery points would create 5 mana. Alternatively, you may convert mana into sorcery points. For every 3 mana you gain 1 sorcery point.
Activating Class or Race Features. You may use mana to regain uses of a limited racial or class features. The cost depends on the recharge: 5 mana for a feature that is recharged during a short rest, 10 mana for a feature that is recharged during a long rest. This is an untested feature, so I may be placing limitations on its use during play. (The goal of this ability is to give non-spellcasters a use for their mana. A fighter being able to recharge their Second Wind feature, or a member of the Dragon tribe being able to re-use their Aura.)
The purpose of using mana is to give the players more control over when they decide to rest. A spellcaster can keep up the fight, a winded fighter can keep going, and hijinks can ensue. You won't have to feel like, "I'm out of spells, I'm done for the day." Instead you can proudly say, "Let's take a break so I can recover my MP."