Lethel, Necro-Born Guardian

Defender, Deathtouch
When this creature would attack, exile target
artifact a player controls. If that artifact is
legendary, this creature gets +4/+4 and loses
defender until end of turn. If not, it gets +1/+1
and loses defender instead
This creature gets +4/+4 if you have 6 or more
Swamps in play