In certain comic arcs, Heimdall tragically meets his end. The circumstances and reasons for his death can vary depending on the specific comic series and plot.
Another theme is the exploration of power dynamics. Heimdall has his own powers and responsibilities, and when paired with an OC, it can create an interesting dynamic. Sometimes the OC might be in awe of Heimdall's power, or they might challenge him, leading to a more complex relationship.
In Heimdall x Reader fanfiction, a common theme is the struggle against fate. Heimdall may know the reader's fate, and the reader may try to change it, which creates conflict and drama. Another theme is the idea of seeing and being seen. Heimdall's all - seeing ability makes this a central aspect of the relationship. He sees the reader in a way no one else can, and the reader may strive to understand him in return. Additionally, the theme of sacrifice can be present. Heimdall might have to sacrifice something for the reader, or vice versa, as their relationship deepens.
Their interaction would be tense at first. Young Kratos, full of energy and unbridled aggression, might see old Kratos as a threat or an obstacle. Old Kratos, on the other hand, would be more reserved and cautious. But as they start to communicate, they would find common ground in their shared past and their connection to their family.