The Dragon Lady has items

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If you want to try out different sets or different units, go into the floating tower in Debir (Orcs on the March). You can purchase units and spells for 0 gold in all levels, to use against the enemy hero on every level. It's a fun "Game" in the game, as the Caretaker puts it. Plus, he says all your dead units will be resurrected in the end. I am only level 2 yet so have not tried (the first enemy is level 7.) Basically, you can try out different unit combinations there.