Vliesmähnen-Löwe

{3}{G}{W}: Monstrum 1. (Falls diese Kreatur nicht monströs ist, lege eine +1/+1-Marke auf sie und sie wird monströs.)
Solange der Vliesmähnen-Löwe monströs ist, hat er Fluchsicherheit und Unzerstörbarkeit.

León melena de lana

{3}{G}{W}: Monstruosidad 1. (Si esta criatura no es monstruosa, pon un contador +1/+1 sobre ella y se convierte en monstruosa.)
Mientras el León melena de lana sea monstruoso, tiene las habilidades de antimaleficio e indestructible.

Lion à crinière bouclée

{3}{G}{W} : Monstruosité 1. (Si cette créature n'est pas monstrueuse, mettez un marqueur +1/+1 sur elle et elle devient monstrueuse.)
Tant que le Lion à crinière bouclée est monstrueux, il a la défense talismanique et l'indestructible.

Leone Vellocriniera

{3}{G}{W}: Mostruosità 1. (Se questa creatura non è mostruosa, metti un segnalino +1/+1 su di essa e diventa mostruosa.)
Fintanto che il Leone Vellocriniera è mostruoso, ha anti-malocchio e indistruttibile.

羊毛鬣のライオン

{3}{G}{W}：怪物化１を行う。（このクリーチャーが怪物的でないなら、これの上に＋１/＋１カウンターを１個置く。これは怪物的になる。）
羊毛鬣のライオンが怪物的であるかぎり、これは呪禁と破壊不能を持つ。

Leão da Juba Lanosa

{3}{G}{W}: Monstruosidade 1. (Se esta criatura não for monstruosa, coloque um marcador +1/+1 nela e ela se tornará monstruosa.)
Enquanto Leão da Juba Lanosa for monstruoso, ele terá resistência a magia e será indestrutível.

Fleecemane Lion

{3}{G}{W}: Monstrosity 1. (If this creature isn't monstrous, put a +1/+1 counter on it and it becomes monstrous.)
As long as Fleecemane Lion is monstrous, it has hexproof and indestructible.

Pioneer Masters

Forgotten Realms Commander

Commander 2017

Theros

An ability that triggers when a creature becomes monstrous won't trigger if that creature isn't on the battlefield when its monstrosity ability resolves.

Monstrous isn't an ability that a creature has. It's just something true about that creature. If the creature stops being a creature or loses its abilities, it will continue to be monstrous.

Once a creature becomes monstrous, it can't become monstrous again. If the creature is already monstrous when the monstrosity ability resolves, nothing happens.