Realm: Arcania (The Surface Realm)
Race: High Elves
Approach: Diplomatic
Think about who and what we are. What are our strengths and weaknesses? What are others' strengths and weaknesses.
We're magical (might) and Diplomatic (elegance), plus we give fertility / healing, lessen sickness, etc.
Elves have domesticated beasts, personally are fragile / (not as fertile or healthy?) and have a realm full of life (we're a life dragon).
Think about it. We compliment each other perfectly and offset each other's weaknesses while playing to strengths.
We use a diplomatic approach (our elegance) and maybe magical (might). Us just being around makes everything better (more fertility and healing with less sickness). So that's something to offer right away, by helping the elves and their domesticated beasts. Plus we can probably help them with whatever they grow or hunt for food, or if they have herds or whatever. It is in the elves' best interest to be nice to us. In return, they should want to make us comfortable, because they have every reason to. We should be seen as at least equals and perhaps superior to them in time.
Short term: Show the elves the blessings we bring, healing (no sickness), fertility, abundance. It is wonderful to be in the presence of a generous life dragon. Bring us your sick, your wounded, you of the frail folk. All life is precious, your kin and kind, your beasts, all. Show us your suffering and we will aid it. This immediately shows the benefits we give with no downside. The will ask us to stay. There is little downside to our being there as we make growing food easier including any we eat. We respect and protect the elves, because we are a life dragon. It is literally what we do.
Long Term: Keep it up and earn their devotion. We ask for such simple devotion and give such wonderful gifts. The lives of elves are precious to us and it pains us when they pass away (literally it's in our description for life dragon). Show the elves to turn their frailty to firmness. May the elves craft armor as scales. May they make swords as claws and spears as fangs. Let the elves be a beacon of life under our guiding banner. May they spread and show life to the other races.
Their arrows are our barbs, biting barbarians back. Their beasts: our bite.
Their spells are our blessings and bile (poison) beating back belligerence.
Our brood shall buttress life, the blessed (half dragons?) shall bolster life.
We are the life dragon. Long live life.
***
As in the previous example, be very polite and respectful of all elven customs we know of. Do not harm anything or come off as threatening. Simply ask politely to speak to their leader, whoever that may be. Explain our case, that we are the life dragon and love the long lived elves and their ways. We detest sickness and death. Ask to see their wounded, their ill and heal them (elf or beast). Be of benefit to the elves and hint that we make food easier to produce and may like some. Moreover, dragons do like having lairs....
We will give them more beasts (fertility boosts). We will cure their sick beasts and their sick friends. We shall aid their crops.
The elves will see us as a good ally, curing their ill, giving fertility to the fragile. The elves are a good people and will clearly see the benefit of being our allies. They will not betray us, because it is not in their best interest to do so. Also, we won't betray them, because it hurts us when they die (and they know this). What elf wouldn't want us to be on their side? Less sickness, more fertility for a fragile folk, high magic? Yes please.
Also we are a green dragon and would probably blend in well in the wilderness with all that green. We may even work our way into their religion. If anybody is going to worship life, it's probably the elves? In time we shall grow our brood and our subjects, as life is wonderful. They shall both be firm. Perhaps the elves will cooperate with the humans or the centaurs in time? There are so many threats to life among these realms so we shall strengthen life under our guiding banner in time.