"Magic is a force interacting with physical forces."
For those who need elaboration, you utilize mana to draw influence to alter elements behavior/shape or reach, but it still operates as it should in real life. The only exception to this is lightning and light, which travels slower due to drawing it, increasing their density, making them "Hard" variants. There is a suspension of disbelief, and then there is rolling your eyes. Regardless of race, your body is susceptible to forces, resiliences must make logical senses, and the vessel can break just as easily as on earth. No amount of "steel" bones will protect your soft organs or muscles. So no, "tanks" do not exist biologically in real life, so they won't here as well. Speeds are realistic; you will not traverse the battlefield at Mach 2 due to biological limitations.
To build upon this, Fire burns; shadows don't hit you in the scrotum. So your flames can't freeze, and shadow/darkness magic can only blind. Lastly, you are not immune to the effects of your attacks. Make a boom, and you're within the blast; you just killed yourself. Send out lightning, and you are both standing on a wet or metallic surface; you just killed yourself. The only exemption is toxins you produce biologically, and the heat or cold of your elements. Lastly, you can only manipulate what your character can feasibly know in-universe. I'm glad you're a theoretical physicist, a chemist, or an evolutionary biologist. But, your OC isn't. Bringing real world knowledge, be it mastered or googled, fits under our definition of Metagaming.
--Schools of Magic--
(You are not restricted to what is in here, these are just examples.)
Elemental magic- The bending of the elements to your will via chi/magic/energy. Fire, Earth, Water, Lightning, Air, Light etc.
Necromancy- The reanimation of undead thralls to your aid. (One smart, up to 5 utterly brainless.) The grafting or manipulation of dead organic material to sow on extra limbs, for example.
Binding- The summoning of magical beings such as elementals or wolves, or other animals manifested using energy. Short-lived, same limitation as necromancy
Illusion- Weakest school of magic can only create a single sensory deception—an image or casting a sound like a ventriloquist behind a character to fool them.
Alchemy- Using reagents and your mana to create and activate explosives or other such effects. Regen, healing powders, spells take too long to work in battle. And any spells that do, will cost 50% of your total mana. The regen of entire limbs in combat not allowed.If you wish to avoid the 50% cost, healing/regen takes ten turns in combat. And can't be used when casting other spells. For example, gashes, minor fractures, scrapes, burns, lesions, and purging toxins. If you are wondering why you can't regrow a limb or something crazy, cancer.
Flesh- The altering of your mass, bone, muscles, fat, or any part of your body. Increase strength, explode bone, enlarge, and shrink (Limited to 50% original height one per day.) And the use of blood and bodily fluids in containers to send out boiling a gout or mist. This is a Giant only skill set due to culture and evolution. (In universe lore reasons.)
Limitations. A character can only utilize two schools or elements. An exception may be made, but only for very long-running characters and is up to mod discretion. For example, you can be a necromancer and an ice mage: a fire or earth bender, Flesh magic, and earth. You can not be a necromancer, fire, and ice. Or flesh, necromancer, and illusionist.
Now onto everyone's favorite part, what powers are banned?
Teleportation/Portals/Space/Time Manipulation/Black Holes
Shadow/Darkness outside what darkness do IRL
Telekinesis/Mental charms/ Mind Control/Mind Reading or Fears
Controlling a character's body or drawing out their energy or soul.
Instantly lethal or debilitating poison and such effects, as they take time to activate in any organism.
Walls for defense due to our power scaling
Walking through solid matter via any means
Omnipresent detection/ Infallible Senses
Perfect stealth to senses
Spirits (No afterlife)/Unholy/Holy magic (No God, no divinity)/Curses
Animal taming magic