Belleau's Instant Entrenchment

You create a snake-like trenchline up to 60 feet long and 5 feet wide. You decide the layout, created using 10 foot segments. This layout can be of your choosing, as long as each segment is congruent with at least one more. You can also decide how deep each segment is, either 5 or 10 feet from the surface. The bottom and walls are lined with wooden planks.

You are also given the option of creating one 15 by 15 foot underground bunker which must also be connected to the trenchline itself. The trenchline is lined on one side with barbed wire, that is difficult terrain. Any creature that travels through the barbed wire or ends its turn there must make a Dexterity saving throw against your spell save DC or take 1d6 piercing damage.

You can cast this spell again while it is active to maintain the trenchline's existence for another 24 hours. You can create a permanent trenchline by casting this spell in the same location and with the same configuration every day for one year.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the trenchline can have 15 additional feet of trenchline for each slot level beyond 3rd.