The way Take Heart is worded you gain only one instance of X life for X attacking creatures you control, so if cast during the combat phase (if you cast it outside of combat or during someone else's turn you don't gain life) you will gain one instance of 5 life for your five attacking creatures and Ajani's Pridemate will get one +1/+1 counter.
February 28, 2019 2:34 p.m.
You get 1 counter on Ajani's Pridemate because it is a single instance of life gain. If it were something instead like Curse of the Forsaken being on the defending player, you would get 5 individual triggers, thus 5 instances of lifegain and 5 counters.
February 28, 2019 2:36 p.m.
So the spell is the instance. Not the number of creatures. Got it.
Thank you both.
February 28, 2019 2:58 p.m.
Darkmoses - since you seem to have resolved your question, please be sure to hit the "Mark as Answer" button on one of the responsive posts. This helps keep the Rules Q&A section clutter-free and allows future users to quickly identify the answer if they happen to have the same question.