That's a tough call. If you asked me from a purely mechanical perspective, I'd say "Keep it to one type of trigger. At the very least, because making the mechanic less complicated means you can do more complicated things with cards that have the mechanic. The more you front load the mechanic, the less creative you can be before player retention simply runs out."

But you're thinking about this from a flavor perspective, and that can chuck a whole barrel of monkeywrenches into the machine.

Personally, I think if you want to say that Elevate switches "simply because of a heroic deed or being at the right place at the right time," then you should do that exactly. Don't do half-measures by looking for purely mechanical triggers like "X number of creatures in a zone." Put some story in there like:

Elevate -- Whenever a Legendary Elf dealt damage by Orc Marauder dies, if Orc Marauder doesn't have a Legend counter on it, put one on it.
As long as Orc Marauder has a Legend counter on it, it gets first strike, and is a Legendary Creature named "Orfbar, Slayer of Princes".

What is the point of elevate?
Why is a creature with it more fun than one without it?

Does this wording make sense? The condition would change for each creature, but they all need the clause about controlling other cards with the same name for obvious reasons.

@jmgariepy: I like the lineage idea, but maybe it should differ by character, as some characters become legendary not because of any special lineage but simply because of a heroic deed or being in the right place at the right time. Some characters could check cards in graveyard, some could check whether they are enchanted, or whether their controller has X or more life, etc. Is this too complicated, or is it fine as long as the cards at common have relatively simple conditions?

Thanks for the help, that makes sense.

Wizards made a very great distinction in Mirrodin Besieged between the commons with battle cry, which had very unimpressive stats like Kuldotha Ringleader and Loxodon Partisan, and the uncommons-and-rares which were very much more aggressively costed - Accorder Paladin, Goblin Wardriver, Signal Pest, and the mythic Heroes Hero of Bladehold and Hero of Oxid Ridge.

So this is entirely on par with the common printed cards with battle cry. Seems to be balanced fine to me. Reasonably powerful in limited; the 2 toughness is a sensible choice, so the opponent can trade a random 2/2 with it at the cost of taking increased damage from all your other creatures for a turn.

I'm trying to pin down what happens in the books that makes a person Legendary. Tolkien has full lineages for some rather minor characters. What about them makes them so special? Is it about being able to trace one's lineage? Would this make sense?:

Gorbag's Lineage (As long as there are two cards named 'Orc Hobbitnapper' in your graveyard, this creature gets +2/+2, is Legendary, and is named Gorbag.)

Alternatively, the card could say "As long as you have a card in your sideboard named "Gorbag". Personally, I think that makes for interesting deckbuilding decisions in both limited and constructed. But it assumes that sideboards are important to you, and they may not be. It doesn't convey as much story as two dead orcs do.

Both this and the Loxodon make Accorder Paladin look godly — although maybe that isn't that far from the truth.

Seems similar to Champion of Arashin in that both lifelink and battle cry are both rather powerful abilities.

Is 3/2 too good? I figured taking 2 toughness and away from Loxodon Partisan would be alright, but I wasn't sure.