I considered variants on the now-iconic "becomes a 0/4 wall creature". Fortifications should usually be walls for flavour, but if there's too many defenders, the board will clog up. This is my attempt to make a wall that can attack.

Obviously a hard-to-kill 3/3 may not be common, but we're looking for any fortifications that might be, and I think this might be.

This uses the same "sacrfice a creature". That's also relevant because it means you're less likely to attack with this, then equip it to another land to block with (which is fun, but more complicated). And you might plausibly have a 1/1 or 2/2 you're happy to upgrade, even at the loss of one net creature.

I wasn't sure about the defender restriction. I thought it made sense it was sometimes a defender, for flavour, but often could attack, so it didn't just promote board stalls. But I'm not sure what the condition should be.

Perhaps just the Walking Wall / Gargoyle Sentinel / Tidewater Minion approach: "Fortified land is a 3/3 Wall creature with defender. // : Fortified land loses defender UEOT."

I wasn't sure if it looked too fiddly to say "has defender" and "loses defender" right next to each other, but yes, I think that's probably about the correct functionality.

Decent card. The funny thing is, that this is such a small improvement on many creatures, that this could almost be costed at ... if it was an uncommon, I suppose it would.

Maybe we can have a wall 'mechanic' that speaks to being a wall, but isn't defender. Like "gains +0/+2 when blocking". I admit, however, that some people will be confused about all these attacking walls. I'd suggest making a new creature type, but I don't think we'll come up with something that gets idea across better than 'wall'.