1. Gain Experience Through Combat
Just like your character, mercenaries earn experience points (XP) by participating in Diablo 4 Gold combat. The more battles you engage in, the more experience your mercenaries gain, eventually leveling them up. However, simply engaging in combat isn't always the most efficient way to level them up. Here are some tips to maximize XP gains:

Combat Strategies for Efficient Leveling:
Fight Together Regularly: The more your mercenary fights alongside you, the faster they will level up. Take them on dungeon runs, world events, and boss fights to maximize XP gain.
Choose High-Density Areas: Areas with a large number of enemies or elite monsters provide more opportunities for combat, thus allowing your mercenaries to gain more XP. Helltides and Strongholds are excellent for farming XP in high-density regions.
Special Quests and Events: Certain quests or world events reward additional XP for mercenaries. Participate in World Boss Events or Gathering Legions, which often spawn multiple enemies at once, ensuring fast kills and more experience.
2. Leveling Up Mercenaries with Special Items
There are specific items in Diablo 4 that can be used to boost your mercenaries’ level more quickly.

XP-Boosting Items:
Tomes of Experience: These consumable items grant a certain amount of XP to your mercenary when used. You can find them as drops from enemies or craft them using materials.
Mercenary Experience Scrolls: Special items that grant a large boost to your mercenary's XP bar when used. These items can be purchased from NPC vendors or found as loot.
XP Potions: These potions grant an experience boost to both you and your mercenaries for a limited time. While they are typically consumed by your character, mercenaries can benefit from the experience bonus during the effect duration.
Using these items strategically, especially during high-intensity combat scenarios, can accelerate the leveling process and help you hit higher levels faster.

3. Completing Mercenary-Specific Quests
Certain mercenaries have unique quests associated with their leveling. These quests are designed to help increase your mercenary’s loyalty to you while also offering XP rewards.

Mercenary Quests:
Progression Quests: Some mercenaries have their own unique progression quests, which reward you with experience points upon completion. These quests might involve clearing certain dungeons, defeating a number of enemies, or participating in world events.
Bonding Quests: Completing quests that deepen the bond between you and your mercenary will not only unlock new abilities but also provide substantial experience bonuses.
Reputation Gains: Some mercenaries can be upgraded through Reputation systems tied to specific factions in the game. Completing faction-related activities will reward you with both faction reputation and experience for cheap Diablo 4 Gold your mercenaries.