Wall of Lava

You create a wall of lava on a solid surface within range. You can make the wall up to 100 feet long and 30 feet high, or a ringed wall/dome up to 50 feet in diameter and 30 feet high. The wall is 3 feet thick. It is opaque from the side of the wall the caster is on, sheds dim light for 30 feet, and lasts for the duration.

When the wall appears, each creature within its area must make a Constitution saving throw. On a failed saving throw, a creature takes 8d8 fire damage and is restrained by the magma wall. On a success, it takes half damage and it is pushed out of the wall's space. Any creature that ends its turn within 5 feet of the wall takes 4d8 fire damage. This fire magic is severe, and its damage bypasses/ignores fire resistances, but not fire immunity. 

Creatures can enter and move through the wall, but they must spend 10 feet of movement for every 1 foot moved through it. A creature that enters the wall's space for the first time on a turn or ends its turn there takes 8d8 fire damage and must succeed on a Constitution saving throw or be restrained by the wall. A restrained creature can use its action to make a Constitution check against your spell save DC. On a success, it frees itself.

This spell ignites flammable objects in the area that aren’t being worn or carried.

Obsidian. Spells that deal more than 20 cold damage and pass through the wall cause the wall to freeze into solid obsidian glass where the spell passed through it (at least a 5-foot square section is frozen). Each 5-foot-square obsidian section has AC 18 and 30 hit points and is vulnerable to thunder damage. Reducing an obsidian section to 0 hit points destroys it. When a section is destroyed, the wall’s lava doesn’t fill it.

If you maintain your concentration on this spell for its entire duration, the wall hardens permanently into obsidian glass instead of vanishing, and it can’t be dispelled. Without the spell's magic to maintain them, the destruction of the panels might now cause other connected panels to collapse at the DM’s discretion.

The wall is an object made of obsidian stone that can be damaged and thus breached. Each panel has AC 18 and 30 hit points per inch of thickness. Reducing a panel to 0 hit points destroys it and might cause connected panels to collapse at the GM's discretion.

If you maintain your concentration on this spell for its whole duration, the wall becomes permanent and can't be dispelled. Otherwise, the wall disappears when the spell ends.