A lot of players don't notice the promotion system until mid-game, and by then they've already made skill choices that lock them out of the path they wanted. Worth understanding early.
How it works
Click the class icon on your hero's screen. You'll see two promotion options — each one is a different direction you can take that hero's identity. One might lean into combat, the other into spellcasting, or utility, depending on the base class.
To unlock either promotion, you need to meet a set of five specific skill requirements. Each of those five skills has to be leveled to Rank 3 — the maximum individual skill tier. Once all five are maxed, the promotion becomes available.
That's the system. It's simple on paper.
Why it's actually hard
Your hero has a limited number of skill slots. You can't just learn every skill and wait — you'll run out of room before you get close to meeting the requirements for anything.
This means every skill you pick up is a commitment. Take a skill that isn't part of any promotion path you care about, and you've spent a slot that could have been reserved for something that matters. Do it two or three times and suddenly the five skills you need won't all fit, even if you theoretically have the levels to rank them up.
The constraint is the point. Promotions are meant to be something you build toward intentionally, not something that happens by accident.
What this means in practice
Before you start leveling a hero seriously, look at both promotion paths for their class and decide which one you're aiming for. Then check which five skills that path needs.
From that point, treat those five skills as your core priority. When you're offered new skills on level-up, always ask whether the option fits your path or burns a slot you need. Passing on a skill that looks good in isolation is often the right call.
The other thing worth knowing: the two promotion paths for the same class will often share some skill requirements and diverge on others. If you're early enough, it's possible to keep both options open for a while by prioritizing the overlapping skills first. At some point you'll have to commit, but delaying that decision gives you more flexibility as you figure out what you actually need.
The system rewards players who look ahead. If you're investing in a hero for the long run — especially one you plan to carry into the late game or PvP — knowing their promotion path before you start assigning skills is one of the better uses of five minutes at the start of a map.