Lets make this simple Your carry is a physical damage dealer and the other not , Solar crest enemies . Your carry is magical damage dealer , Solar crest him . Both ally and enemy are physical damage dealer , then it depends on the armor values of both heroes , since armor is more worth if you have little a hero with 40 armor wouldn ' t care to get 10 or 10 , a hero with 10 armor would benefit a lot with the 10 armor , so if your carry has say 15 armor and the enemy carry has 25 you should use solar crest on ally even if that ally is a physical damage dealer . When both heroes have lots of armor , it is better to use Solar crest on the enemy . In the example you made , Sven gets lots of armor with his warcry , so he usually has like 30 armor , giving him more armor is not worth it , reducing the armor of the enemy Sven to 20 is not a lot too , but it is better to reduce armor from heroes with high armor than to give more armor to heroes with a lot of armor .