There are "test dummy" monsters in Prontera (as of relatively recently): npc/re/mobs/towns.txt
//==================================================
// Prontera, Training Dummy Area
//==================================================
prontera,251,77,0,0 monster Dummy Lv50 2409,1,5000,0,0
prontera,259,77,0,0 monster Dummy Lv50 2409,1,5000,0,0
prontera,251,66,0,0 monster Dummy Lv100 2410,1,5000,0,0
prontera,259,66,0,0 monster Dummy Lv100 2410,1,5000,0,0
prontera,251,55,0,0 monster Dummy Lv150 2411,1,5000,0,0
prontera,259,55,0,0 monster Dummy Lv150 2411,1,5000,0,0