In my project...mage class abilities are based on the current environment.

In a forest - earth and wind abilities
In a forge or factory - Fire and Dark abilities
River or ocean areas - water and wind
etc

Also area specific abilities come to all the classes...like if your in a warehouse...the warrior class can toss barrels or crates at the enemies to stun them...only x amount of times per battle.

Or on a wooden bridge the mage class can shake the bridge violently and cause both allies an enemies to lose footing and become stunned for a turn.

But i'm a little on edge on what elements to give the mages while inside a basic building.

Wooden Cabin - earth? wood? toss a couch?
Castle - earth? stone? animate a suite of armor?

not as simple as using outdoor mechanics.

The mage class is the most role changing class in the game by far. For it can go from healer > tank > support > damage depending on what environment the group is in.

Just seeing if I could draw inspiration.

Thanks in advanced.

I suppose it really depends on what type of house it is. Is it an old abandoned shack? Maybe they could(once per battle, maybe) cause the roof or some support beams to collapse and damage all enemies, or the floor to crack and trip them. Or in a better cared for house, they could toss furniture , or shatter windows to surprise them. It really depends on what type of house we're talking about.

As for elements, I'm not really sure.

Earth, simply because almost all houses (even to modern day) are made from earthen materials. Primarily wood, but also includes glass and steel.

Interesting ideas...thx for the responses

Basic cabin like house

Roof Cave in - does damage to all enemies
Shatter Window - Chance to Daze all enemies
Earths Grasp - Binds Target to the ground...prevents them from using non ranged attacks for 1 turn
(If fireplace not lit )Smoke Screen - chance to cause Blind status effect

Castle

Earths Grasp - Binds Target to the ground...prevents them from using non ranged attacks for 1 turn
Stone Sentry - Greatly increase defense but drastically reduces agi str dex and mnd....also causes enemy's to focus on you
Animate Suit of armor - summons a suit of armor ally that forces all enemy's to attack it for up to 3 turns if it doesn't die...only once per battle
Magic Carpet - Caster gains float effect - immune to sweep or earthquake like effects

Feel free to add some ideas

I assume you're doing this by Terrain ID?

^
No actually, I don't have random battles. Each Battle is evented and therefore given the chosen set of abilities.