Is that dragon soul worth it? Assessing the significance of neutral objectives in League of Legends via Gradient Boosting Classifier

image from
  • the first two dragons compared to the rift heralds?
  • the third and fourth dragons compared to Baron Nashor (“baron”)?
  • the baron compared to the Elder dragon?

VERY Brief Overview of Game Knowledge

What are neutral objectives?

  • Before the 20 minute mark when Baron first spawns, the rift herald is available for capture in the baron pit. The rift herald damages and helps in destroying turrets, which also gives gold resource rewards.
  • After the 20 minute mark, Baron Nashor spawns and will buff the killing team players and minions temporarily
  • Elemental dragons grant different advantages depending on the type of dragon: infernal — offensive damage, mountain — defensive stats and shield, cloud-cooldown reduction, ocean — health and mana regeneration. Elemental dragons repeatedly spawn until one team collects 4 dragons total, which will grant that team dragon soul, a much stronger version of the individual dragon buff.
  • After dragon soul is taken by a team, elder dragons will spawn instead. Elders are intended to help teams close out games with serious combat buffs. It buffs the teams’ players with extra damage and will automatically execute enemy players that drop below 20% health.
Fig 1. Summoner’s Rift. with labelled monster objectives. You can always check out a guide for a comprehensive introduction to the game.

Neutral objectives pose in-game dilemmas on the fly

Predicting League of Legends Game Outcomes

Project Overview

Predictive Models

Data Extraction from Riot API

Evaluation Metrics

Data Preprocessing

Fig 2. Example of a Pandas dataframe of neutral objectives for one match

Imputing with means

Initial look at match data

Removing “remakes”

Quick Look at Game Lengths

Histogram of match lengths

How common are objective events?

Fig 4. How common are objective events?
Fig 5. Proportion of matches still running and % of games with no objective events at various time intervals.

Win Distribution

Initial correlation heatmaps

Correlation heatmap of in-game objective stats (at specified match time) with the winning team

Model Selection

Comparison of ensemble learning algorithms

Model Tuning

  • max_features: range(1, 9) 4
  • min_samples_leaf: range(1, 9) 6
  • criterion: [“gini”, “friedman_mse”] friedman_mse
  • n_estimators:[10, 20, 60, 100] 60
  • learning_rate: [0.05, 0.01, 0.1, 0.2, 1] 0.2
  • max_depth: [None, 1, 3, 5, 10] 5
Accuracy and F-score of the post-game predictive model, before and after RandomSearchCV optimization
Change in model performance for each in-game time interval

Extracting Feature Importance

Feature importances of game variables at every in-game time interval
Post-game Feature importances
  • Which team kills the first inhibitor seems to be the best predictor of who will win the game. This makes sense since killing an inhibitor is the most direct path towards killing the enemy nexus. The first inhibitor kill accounts for 40% of the weights for predicting the game winner.
  • The difference in elemental drakes taken by a team is the next best predictor. Without doing further analysis it’s hard to say whether this difference is statistically significant. We can speculate that if one team is successful at capturing dragon objectives, they likely have a strong control over the game carrying over to wins.
  • 10 mins: elemental dragon differences, in order of Ocean > Infernal > Mountain > Cloud.
  • 15–20 mins: rift herald difference — if the rift herald is captured early enough, it will spawn a second time as a stronger buff. The rift herald will despawn at 20 minutes if not killed, so the window of most significance during 15 and 20 minutes reflects this nicely. The 20 minute association is stronger than the 15 minute one in accordance with the rift herald’s strength.
    - 25–35 mins: Baron nashor difference — at 35 mins, soul dragons and elder dragons become more significant, but their effects are still overshadowed by literally every other objective.

Elemental Dragons

Future Directions

  • add other relevant match variables: team gold, kills, wards, champion picks, lane positions, etc.
  • try fitting a XGBoost Classifier model, a variation of the Gradient Boosting Classifier used for the project
  • expand dataset — due to time practicality limitations, only 20,000 matches were extracted from over 60,000 match IDs obtained. Also interested in expanding to other servers— e.g. EU, China, Korean — and to lower elos; masters+ is a very small proportion of the playerbase and may not reflect what the predictors are in lower elo (e.g. Bronze, Silver, Gold)
  • evaluate competitive play, which plays out differently than solo queue, and where objective decisions matter more than anywhere else



Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store