Two type of trap. Flame Trap and Net Trap. Both are craftable under Machine.
Each trap have 3 rank. I, II, III.
Net Trap I = Enemy trigger it and get trap that turn. Lose next turn. Return to normal.
II = Enemy lose 2 turn.
III= Enemy lose 3 turn.
Flame Trap Ranking is just for higher damage I think. Never use them.
You must have the trap in your inventory.
In TBS, you select the trap you want to use, and click it on the ground area. Some area you can't put and some you can. The trap last 10 turns then disappear. It takes 1 turn to set the trap.
Here some screenshot on example of using trap at bottom.game-strategies-f7/topic795.html
You have to start Base Camp training 1 in order to start Training Hall 1 upgrade. Base II for Training II and so forth.
Not sure about this yet. Maybe later when there are multiple Base Camp, you can set where you want to resurrect your dead merc.