Heroes of Loot

As you play through the game and kill enemies, you will gain experience. This trophy will pop once you reach XP level 10. Note that completing Quests, and finding Scrolls (can be purchased or found in secret rooms) will also boost your XP. Certain characters also earn XP quicker than others. In any case, regardless of which you choose, you will reach XP 10 before killing enough enemies to earn Slay 5000 Monsters.

Note that XP does NOT carry over between playthroughs, so if you die, you will restart at XP level 0.